“Check-in” is the hyphenated noun for registration or the place/process where it happens. “Check in” is the two-word phrasal verb used when someone registers or reports arrival.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “check-in” as the noun for the act, process, or place of registering arrival. Use “check in” as the verb, as in “Please check in online.”
Key details
Confusion Familyword-boundary
Noun Variant ScopeCambridge places the hyphenated noun “check-in” and the two-word phrasal verb “check in” in the same entry, making the word-class boundary explicit.
Rule Familyorthographic-boundary
Termscheck-in, check in
Choose the right form
Decision table for Check-in vs. Check In
If you mean / need
Use
Why
the registration process or area
check-in
Cambridge records the noun with a hyphen.
the action of registering or reporting arrival
check in
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 places the hyphenated noun “check-in” and the two-word phrasal verb “check in” in the same entry, making the word-class boundary explicit.
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.
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