group vs gang

group and gang both are nouns.

Word	Noun	Adjective	Verb	Adverb
group	Yes	No	Yes	No
gang	Yes	No	Yes	No

As verbs, gang is a hyponym of group; that is, gang is a word with a more specific, narrower meaning than group:

Other hyponyms of group include team, team up, embed, gang up, pool, brigade.

group (noun)	gang (noun)
any number of entities (members) considered as a unit	tool consisting of a combination of implements arranged to work together
a set that is closed, associative, has an identity element and every element has an inverse	an organized group of workmen
(chemistry) two or more atoms bound together as a single unit and forming part of a molecule	an association of criminals
	an informal body of friends

group (verb)	gang (verb)
arrange into a group or groups	act as an organized group
form a group or group together