“Callback” is a noun for a return phone call, a later audition or interview, or a reference to something earlier. “Call back” is a phrasal verb, including phoning someone again or returning to collect or see something.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “callback” for the noun (“I’m waiting for a callback”) and “call back” for the verb (“I’ll call you back”).
Key details
Confusion Familyword-boundary
Rule Familyorthographic-boundary
Termscallback, call back
Choose the right form
Decision table for Callback vs. Call Back
If you mean / need
Use
Why
a return call, second audition/interview, or reference as a thing
callback
It is the noun.
the action of phoning or returning again
call back
It is the phrasal verb.
Further guidance
Core difference
“Callback” names the thing or event; “call back” expresses the action.
Fast Test
If you can conjugate it—“called back,” “calling back”—use two words. If an article can precede it—“a callback”—use the noun.
Sense Boundary
The noun has several established senses, so this page focuses on the word-class boundary rather than one narrow definition.
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.
