Rules for capitalization and case selection.
An ampersand is meaningful text, not merely decorative punctuation. Chicago normally limits ampersands in edited prose but preserves them in established terms, corporate names, verbatim quotations, and work titles that use the symbol.
APA title case capitalizes the first word, the first word of a subtitle, major words, and words of four letters or more while keeping short minor words lowercase in ordinary mid-title positions.
Apostrophes can mark possession, contractions, or omitted initial letters, and those uses should not be confused with quotation marks. Chicago also has specific title-case examples for initial-apostrophe contractions and for the compound form “O’Clock.”
Chicago 18 uses title case for titles of works and changed a long-standing rule: prepositions of five letters or more are now capitalized. Shorter prepositions generally remain lowercase internally, while first and last words are capitalized and “to” remains lowercase as an infinitive marker in ordinary mid-title use.
Common nouns are ordinary category names for people, animals, places, things, and ideas. They contrast with proper nouns, which identify specific named entities and are conventionally capitalized.
Coordinating conjunctions are a major source of title-case differences: APA lowercases short conjunctions, while current Chicago names a narrower lowercase set and capitalizes “so” and “yet.”
The generic word “email” is normally lowercase in running text and is not hyphenated in Microsoft style. Capitalize “Email” only when ordinary sentence or heading position requires it, or when a proper name or interface label has its own casing.
Email subject lines do not have one universal capitalization rule; the choice depends on message context and house style. Chicago explicitly distinguishes routine correspondence from more formal organizational mailings, so this guide does not label one case style universally correct.
A title appearing inside another title has its own identity and may need quotation marks, italics, or language-specific treatment. Flattening the inner title into the outer title’s token stream can destroy both formatting and capitalization.
Kinship words can act either like names or like ordinary common nouns. Chicago guidance capitalizes forms such as “Mom,” “Dad,” and “Grandma” when they stand in place of a personal name, while generic/descriptive uses are normally lowercase.
Major title-case systems capitalize the first and last words of a title or subtitle even when the same word would normally be lowercase internally. A converter therefore needs segment endpoints, not only a small-word list.
“according to” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
“because of” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
“due to” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
“instead of” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
“out of” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
“up to” is a multiword expression whose title-case result depends on both style and how that style treats the words inside a phrase. Treat the expression as a phrase span while still applying the chosen style’s rule to each component rather than treating the phrase as one indivisible token.
Hyphens and dashes are not interchangeable in title-case logic. Chicago 18 changed the treatment of later elements in prefix-based hyphenated compounds, while an em dash can act like a parenthetical or subtitle-like boundary depending on structure.
Hyphenated compounds cannot be capitalized safely with one universal “capitalize everything after a hyphen” rule. APA explicitly capitalizes the second part of hyphenated major words, while Chicago 18 changed its prefix-compound treatment and still applies grammatical title-case rules to individual elements.
Modern house styles commonly lowercase “internet.” Microsoft’s current style guide explicitly says not to capitalize it. Capitalization can still differ in quotations, proper names, legacy material, or a publication that intentionally follows another style.
APA capitalizes “About” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “Across” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “After” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “Against” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
Along can function as a preposition or adverb. APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
APA capitalizes “Among” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
The word “and” is normally lowercase in the middle of a title because it is a coordinating conjunction, but first-word, last-word, and style-specific rules can change the answer.
Usually lowercase inside a title. “An” is an article and is normally lowercased internally in APA, Chicago, and MLA title case, subject to first/last or subtitle-boundary rules. This guide separates style-specific treatment instead of using one universal small-word list.
APA capitalizes “Around” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
“As” is a grammar-sensitive title-case word. APA normally lowercases it internally because it is a short conjunction or preposition, while Chicago 18 explicitly keeps “as” lowercase in any grammatical function except where a boundary rule independently requires capitalization.
Usually no in the middle of a title. “at” is a short preposition: APA lowercases short prepositions of three letters or fewer, Chicago 18 lowercases prepositions of four letters or fewer, and MLA title style normally treats internal prepositions as minor words. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
Usually lowercase inside a title. APA, Chicago, and MLA treat an internal article such as “a” as a minor word, while first-position and subtitle-boundary rules still capitalize it. This guide separates style-specific treatment instead of using one universal small-word list.
APA capitalizes “Before” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “Between” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
APA capitalizes “Beyond” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
Usually no in the middle of a title. APA lowercases short conjunctions such as “but,” Chicago 18 explicitly lowercases “but” among its common coordinating conjunctions, and MLA title style normally leaves coordinating conjunctions lowercase unless a boundary rule applies. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
Usually no in the middle of a title. “by” is a short preposition: APA lowercases short prepositions of three letters or fewer, Chicago 18 lowercases prepositions of four letters or fewer, and MLA title style normally treats internal prepositions as minor words. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
APA capitalizes “Despite” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
APA capitalizes “During” internally because it has at least four letters. Chicago 18 also capitalizes it because prepositions of five letters or more are capitalized. MLA ordinarily lowercases internal prepositions, while any principal-word use needs grammatical classification before an automated decision.
“For” is normally lowercase in the middle of both APA and Chicago title case when it functions as a short conjunction or short preposition. Position still matters, and a converter should not generalize that answer to unrelated grammatical uses without checking context.
APA capitalizes “From” internally because it has four letters. Chicago 18 and MLA normally lowercase it internally as a preposition. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
APA normally lowercases the short conjunction “if” internally, while Chicago capitalizes subordinating conjunctions such as “If.” This is a genuine cross-style difference, so the requested style matters. This guide separates style-specific treatment instead of using one universal small-word list.
Inside can function as a preposition, adverb, adjective, or noun. APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
APA capitalizes “Into” internally because it has four letters. Chicago 18 and MLA normally lowercase it internally as a preposition. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
Usually no in the middle of a title. “in” is a short preposition: APA lowercases short prepositions of three letters or fewer, Chicago 18 lowercases prepositions of four letters or fewer, and MLA title style normally treats internal prepositions as minor words. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
APA capitalizes “Like” internally because it has four letters. Chicago 18 lowercases it when used as a short preposition but capitalizes principal-word uses such as a verb; MLA likewise depends on grammatical function. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
APA capitalizes “Near” internally because it has four letters. Chicago 18 lowercases it when it is a short preposition but capitalizes adverb/adjective uses; MLA likewise distinguishes minor-preposition from principal-word uses. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
Usually no in the middle of a title. APA treats the short conjunction “nor” as a minor word, Chicago 18 names “nor” among the coordinating conjunctions it lowercases, and MLA title style normally leaves coordinating conjunctions lowercase internally. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
“Off” cannot be assigned one safe capitalization from spelling alone. As a short preposition it is normally lowercase internally in APA and Chicago, but as an adverb or verb particle it is a major word and is capitalized; the surrounding phrase determines the answer.
“Of” is normally lowercase in the middle of a title in APA 7, Chicago 18, and MLA-style title capitalization because it is a short preposition. First- or last-word position can override the ordinary middle-of-title treatment.
Usually no in the middle of a title. “on” is a short preposition: APA lowercases short prepositions of three letters or fewer, Chicago 18 lowercases prepositions of four letters or fewer, and MLA title style normally treats internal prepositions as minor words. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
Usually no in the middle of a title. APA lowercases the short conjunction “or,” Chicago 18 explicitly includes “or” in its lowercase coordinating-conjunction set, and MLA title style normally keeps coordinating conjunctions lowercase internally. The answer depends on the style guide and position, so this page separates APA 7, Chicago 18, and MLA guidance instead of applying one generic title-case list.
Outside can function as a preposition, adverb, adjective, or noun. APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
APA capitalizes “Over” internally because it has four letters. Chicago 18 lowercases it when it is a short preposition but capitalizes it when it functions as an adverb; MLA treatment likewise depends on whether it is functioning as a minor preposition or a principal word. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
Usually lowercase internally. “Per” is a short preposition and is normally lowercased inside a title in APA, Chicago, and MLA, apart from title/subtitle boundary rules. This guide separates style-specific treatment instead of using one universal small-word list.
Since can function as a preposition, conjunction, or adverb. APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
“So” is normally lowercase in the middle of APA and Chicago title case when it functions as one of the short/common coordinating conjunctions covered by those styles. It is capitalized when a positional rule applies, such as appearing first in the title.
“Than” exposes a genuine style-engine edge case. APA capitalizes it because it has four letters, while Chicago 18 may lowercase it as a preposition but capitalize it as a conjunction, so Chicago output can depend on the grammatical structure of the title.
Usually lowercase inside a title. “The” is an article and is normally lowercased internally, but it is capitalized when it begins a title or a subtitle and where a style’s boundary rule requires it. This guide separates style-specific treatment instead of using one universal small-word list.
APA capitalizes “Through” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
Toward and towards are both prepositions. Cambridge describes toward as mainly US and towards as mainly UK. APA capitalizes either spelling internally because each has at least four letters; Chicago 18 capitalizes either because each is a preposition of five letters or more; MLA ordinarily lowercases an internal preposition.
“To” is normally lowercase in the middle of titles under APA, Chicago, and MLA-style capitalization when it functions as a short preposition; Chicago also explicitly keeps “to” lowercase as an infinitive marker in ordinary mid-title position. Edge position can change the result.
APA capitalizes “Under” internally because it has at least four letters. Chicago 18 also capitalizes it when used as a preposition because current Chicago capitalizes prepositions of five letters or more. MLA treatment still depends on grammatical function, so prepositional and principal-word uses should not be collapsed into one rule.
Until and till can both function as prepositions or subordinating conjunctions. APA capitalizes both because each has at least four letters. Chicago 18 capitalizes until, while till needs grammatical-role analysis because a four-letter preposition is lowercased but a subordinating conjunction is capitalized. MLA likewise depends on whether the word is functioning as a preposition or a subordinating conjunction.
APA capitalizes “Upon” internally because it has four letters. Chicago 18 and MLA normally lowercase it internally as a preposition. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
Spell-out “versus” is capitalized in APA by the four-or-more-letter rule and in Chicago 18 because the preposition has five or more letters. The abbreviation “vs.” is kept review-only in automation because abbreviation punctuation and house-style form must be preserved. This guide separates style-specific treatment instead of using one universal small-word list.
Usually lowercase internally. “Via” is a three-letter preposition, so APA and Chicago keep it lowercase in ordinary mid-title position; MLA likewise treats internal prepositions as minor words. This guide separates style-specific treatment instead of using one universal small-word list.
Within can function as a preposition (and in some dictionaries an adverb). APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
Without can function as a preposition. APA, Chicago 18, and MLA do not use one universal “small word” rule; capitalization depends on style and, where the word has multiple grammatical roles, on its function in the title.
APA capitalizes “With” internally because it has four letters. Chicago 18 and MLA normally lowercase it internally as a preposition. This guide keeps style-specific rules separate and marks grammatical ambiguity where the same spelling can play different roles.
“Yet” is normally lowercase in the middle of APA and Chicago title case when it functions as a coordinating conjunction. As with other minor words, title position and grammatical role can override a simple lowercase rule.
List-item capitalization is a style decision that should be consistent within a list. Microsoft’s house style normally starts each item with a capital letter unless a specific reason calls for lowercase.
MLA 9 describes title style as capitalizing the first word, last word, and all principal words. MLA’s public Style Center also documents the traditional lowercase treatment of internal prepositions, but its detailed preposition article is edition-labeled for MLA 8, so this engine does not yet treat the full MLA 9 converter profile as complete.
Multiword prepositions such as “according to,” “because of,” “instead of,” “out of,” and “up to” should not be handled by a single crude small-word list. Different style systems analyze components differently, and some phrases contain words that can change grammatical role.
A colon can create a title/subtitle boundary, but nested punctuation still needs structural handling. Chicago capitalizes the first word after a title/subtitle colon; repeated or nested colons should therefore be parsed as boundaries rather than treated as ordinary word punctuation.
Parentheses can appear in headings and titles without creating a new capitalization system. Chicago says the parentheses themselves are normally ignored when title case is applied, so words inside still follow their grammatical title-case rules.
Part of speech can change title capitalization for surface-identical words such as “than,” “like,” “over,” “off,” and phrasal particles. A reliable converter therefore needs reviewed grammatical context instead of a single lowercase-word list.
Degree abbreviations are style-dependent. Current MLA Style Center material uses “PhD” without periods in editorial prose and author biographies. Other institutions may prescribe “Ph.D.”, so writers should follow the style guide governing the document rather than treating punctuation as a grammar error.
Short words such as “up,” “out,” and “on” can change capitalization when their grammatical role changes. Chicago’s own examples capitalize “Up” or “Out” when those words function adverbially in a phrasal verb, while ordinary prepositional uses can remain lowercase.
Chicago 18 changed how later elements in prefix-based hyphenated compounds are capitalized: each component now follows the general title-case rule. Safe automatic treatment still requires recognizing that the hyphen truly joins a reviewed prefix compound.
Prepositions are one of the clearest places where title styles diverge. APA uses a four-letter major-word threshold, Chicago 18 capitalizes prepositions of five letters or more, and MLA editorial guidance generally lowercases internal prepositions regardless of length.
Some names and work titles intentionally use distinctive casing or punctuation that a generic title-case algorithm should not normalize away. A safe converter needs a reviewed preservation layer and must distinguish a known protected form from arbitrary mixed case.
Colons, semicolons, and dashes can create capitalization boundaries in titles, while quotation marks and parentheses may introduce embedded structures that require additional analysis. This guide separates punctuation-boundary detection from word-class decisions so it can explain when a new segment begins and when it must leave the result unresolved.
Quotation marks do not by themselves decide which words are capitalized. A converter must distinguish harmless outer quotation punctuation from an embedded title or quoted structure that may need its own capitalization and formatting rules.
A slash can join alternatives, words, phrases, or other structures, so the slash itself is not enough information to decide capitalization around it. This guide therefore treats unresolved slash constructions as structural cases rather than splitting and guessing.
The first word of a subtitle is treated as a new capitalization boundary in major title-case systems. APA explicitly capitalizes the first word of a subtitle, Chicago capitalizes the word after a title/subtitle colon, and MLA has published the same treatment in its Style Center guidance.
Good column headers identify the contents of a column quickly and precisely. Microsoft recommends specific labels, sentence-style capitalization, and structures that do not force readers to combine each header with cell text as one sentence.
