“Someone” is the standard one-word pronoun for an unspecified person. The two-word sequence “some one” is possible when “one” remains a separate word and the construction singles out an individual member of a group, so the forms should not be treated as freely interchangeable.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “someone” for an unspecified person; reserve “some one” for constructions where “one” is separately emphasized or selected from a group.
Key details
Confusion Familyword-boundary
Rule Familyword-boundary
Termssomeone, some one
Variant ScopeThe one-word pronoun is standard for an unspecified person; the spaced form belongs to constructions where one remains a separate element.
Further guidance
Core difference
“Someone” is a one-word pronoun meaning an unspecified person; “some one” keeps “one” separate when the wording singles out one member of a group.
Fast Test
If you could replace the expression with “somebody,” use “someone.” If you mean one particular member from a set, the two-word construction may be appropriate.
Usage Boundary
Do not split ordinary pronoun “someone” merely for emphasis; the spaced form needs a real grammatical reason for keeping “one” separate.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
“Anyone” is one word when it means any person. “Any one” is written as two words when the construction refers to a single member of a larger set, including the common pattern “any one of …”.
“Everyone” is one word when it means every person. “Every one” is two words when one is a separate element referring to each individual member of a set, especially in constructions such as “every one of them.”
The standard expression is written “no one,” and Cambridge also records the hyphenated variant “no-one.” The fully closed spelling “noone” is not the accepted form in the cited grammar guidance.
Standard English writes “a lot” as two words for a large amount, number, frequency, or degree. “Alot” is a common misspelling in this sense; it should not be confused with the separate verb “allot.”
“Any more” can be a determiner for additional quantity and an adverb meaning “no longer.” Cambridge notes that the one-word adverb “anymore” is especially common in American English, while the determiner remains two words.
“Blackout” is the closed noun, while “black out” is the two-word phrasal verb. The verb can describe losing consciousness or obscuring/darkening something; the noun names the resulting event or state.
