grouping vs assortment

grouping and assortment both are nouns.

Word	Noun	Adjective	Verb	Adverb
grouping	Yes	No	No	No
assortment	Yes	No	No	No

As nouns, assortment is a hyponym of grouping; that is, assortment is a word with a more specific, narrower meaning than grouping:

grouping: the activity of putting things together in groups
assortment: the act of distributing things into classes or categories of the same type

grouping (noun)	assortment (noun)
any number of entities (members) considered as a unit	the act of distributing things into classes or categories of the same type
the activity of putting things together in groups	a collection containing a variety of sorts of things
a system for classifying things into groups