safety match vs book matches

safety match and book matches both are nouns.

Word	Noun	Adjective	Verb	Adverb
safety match	Yes	No	No	No
book matches	Yes	No	No	No

As nouns, safety match and book matches are synonyms defined as:

safety match and book matches: a paper match that strikes only on a specially prepared surface

safety match (noun)	book matches (noun)
a paper match that strikes only on a specially prepared surface	a paper match that strikes only on a specially prepared surface