“Mock-up” is a hyphenated noun for a model or preliminary layout, with closed “mockup” also documented. “Mock up” is the two-word phrasal verb for making such a model.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “mock-up” for the noun model or layout; Cambridge also records “mockup” as a noun variant. Use “mock up” as the verb meaning to make a model or representation.
Key details
Confusion Familyword-boundary
Noun Variant ScopeCambridge records “mock-up” with “mockup” as a noun variant and separately records the phrasal verb “mock something up.”
Rule Familyorthographic-boundary
Termsmock-up, mockup, mock up
Choose the right form
Decision table for Mock-up vs. Mock Up
If you mean / need
Use
Why
a model or preliminary layout
mock-up / mockup
Cambridge documents both noun spellings.
the action of making a model or representation
mock up
The phrasal verb is written as two words.
Further guidance
Core difference
Use the documented noun or modifier form when naming a thing, result, person, or concept; use the spaced form when the words function as a verb.
Fast Test
If the expression can take ordinary verb tense or inflection in the sentence, the spaced verb form is usually the relevant choice.
Variant Boundary
Cambridge records “mock-up” with “mockup” as a noun variant and separately records the phrasal verb “mock something up.”
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.
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.”
“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.
“Blowout” is a closed noun for several events or results, and Cambridge also records “blow-out” as a noun variant. “Blow out” is the two-word phrasal verb, including the sense of extinguishing a flame.
“Breakout” is a closed noun for an escape and an adjective in several established senses. Cambridge also documents “break-out” in modifier use. “Break out” is the two-word phrasal verb for meanings such as beginning suddenly or escaping.
“Breakthrough” is a closed noun for an important discovery or advance and can also modify a following noun. “Break through” is the two-word phrasal verb for forcing or moving through a barrier or threshold.
“Build up” is the two-word phrasal verb. For the noun, Cambridge records hyphenated “build-up,” while its American dictionary also records closed “buildup.” The noun spelling therefore has a documented regional/style variant rather than one universal form.
