half dozen vs half-dozen

half dozen and half-dozen both are adjectives.

Word	Noun	Adjective	Verb	Adverb
half dozen	No	Yes	No	No
half-dozen	No	Yes	No	No

As adjectives, half dozen and half-dozen are synonyms defined as:

half dozen and half-dozen: denoting a quantity consisting of six items or units

Other synonyms of half dozen include 6, six, vi.

half dozen (adjective)	half-dozen (adjective)
denoting a quantity consisting of six items or units	denoting a quantity consisting of six items or units