Cambridge distinguishes the two-word phrasal verb “mix up” from the hyphenated noun “mix-up.” The candidate spelling “mixup” is therefore normalized to the dictionary-backed noun form rather than treated as the default closed noun.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “mix up” for the phrasal verb and “mix-up” for the noun meaning a mistake or confused situation.
Key details
Confusion Familyword boundary
Rule Familynoun versus phrasal verb
Termsmix-up, mix up, mixup
Variant ScopeCambridge records hyphenated noun “mix-up” and two-word phrasal verb “mix up”; the closed “mixup” is not the form used for the dictionary noun entry.
Further guidance
Core difference
Use “mix up” as the phrasal verb and “mix-up” as the noun for a mistake or confused situation.
Fast Test
If the expression is an action that can become “mixed up” or “mixing up,” use two words. If it names the resulting mistake/confusion, use the hyphenated noun.
Usage Boundary
Do not close the noun as “mixup” merely because similar noun/verb pairs sometimes become closed compounds; Cambridge gives “mix-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.
The spaced form “turn on” functions as a phrasal verb. The noun meaning a person or thing that excites or attracts is commonly written “turn-on”; Collins additionally records a closed American-English noun “turnon,” so the page keeps that variation explicit.
“Lockdown” is the noun for an official restriction or state of restricted movement, while “lock down” is the corresponding phrasal verb. Sentence function determines the spacing.
“Phase out” and “phaseout” differ by grammatical function. Merriam-Webster records “phaseout” as the noun and “phase out” as the corresponding verb, with forms such as “phased out” and “phasing out.”
“Pinpoint” is a dictionary word used as a verb, noun, and attributive adjective. The two-word sequence “pin point” is appropriate only when “pin” and “point” keep their independent meanings, such as referring literally to the point of a pin.
“Touchdown” and “touch down” differ mainly by grammatical function. Cambridge records the closed form as a countable noun for landing and sports senses and the two-word form as a phrasal verb, including aircraft landing and rugby uses.
“Turn off” is the two-word phrasal verb for switching something off, leaving a road, or causing loss of interest. The corresponding noun appears as closed “turnoff” in American usage and also as hyphenated “turn-off” in Cambridge.
