4-membered vs four-membered

4-membered and four-membered both are adjectives.

Word	Noun	Adjective	Verb	Adverb
4-membered	No	Yes	No	No
four-membered	No	Yes	No	No

As adjectives, 4-membered and four-membered are synonyms defined as:

4-membered and four-membered: of a chemical compound having a ring with four members

4-membered (adjective)	four-membered (adjective)
of a chemical compound having a ring with four members	of a chemical compound having a ring with four members