mass
The word you are looking for is "mass."
A large group of something that rhymes with "lass" and is a four-letter word is "mass." In physics, mass refers to the amount of matter in an object, typically measured in kilograms. It is a fundamental property of an object that determines its inertia and gravitational attraction.
team
Quad or its derivatives refer to four of something or a forth part of something. A group of four people is called a quartet, one of these would be a quarter of the quartet
it is a fact that fact rhymes with tact
Clan heir
slab
more so
floor
Four
The term Tetrad means a group of four. It can be used in any context when talking about something that has a collective of four such as a tetrad of cats.
mountainberry