No, the word 'username' is a compound noun, a singular, common abstract noun.
A collective noun is a word used to group like people or things; for example a collective noun for 'username' could be: a list of usernames.
Shoal is a collective noun. It is the collective noun for fish. A shoal of fish.The collective noun is a mint of candies
The collective noun is a series of explosions.
There is no standard collective noun for a group of reflections. The noun 'reflection' is not a standard collective noun.
No, the noun lumber is not used as a collective noun. The collective noun for lumber is a stack of lumber.
No, the noun land is not a collective noun. However, any noun can function is as a collective noun in a suitable context without being a designated collective noun.
No, the noun farm is not a collective noun.
The collective noun for 'wheat' is a sheaf of wheat.The collective noun for 'barley' is a crop of barley.
The collective noun is a drift of icebergs.
No, games is not a collective noun. The collective noun for games is 'a compendium of games'.
The collective noun is an anthology of poetry.
No it is not a collective noun.
No, the noun 'kin' is not a collective noun.