group vs aggroup

group is a noun but aggroup is not a noun.

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

As verbs, group and aggroup are synonyms defined as:

group (noun)	aggroup (noun)
any number of entities (members) considered as a unit
a set that is closed, associative, has an identity element and every element has an inverse
(chemistry) two or more atoms bound together as a single unit and forming part of a molecule

group (verb)	aggroup (verb)
arrange into a group or groups	form a group or group together
form a group or group together