These are the words to talk about groups of things. These words come from Latin. These are for general use. There is also more scientific set, for chemistry.

1 = solo
2 = duet (or duo, or pair)
3 = trio
4 = quartet
5 = quintet
6 = sextet
7 = septet
8 = octet
9 = nonet

These words can be used to replace the phrase “group of #”. For example, “a group of 8 birds” can be replaced with “an octet of birds”. This is most commonly used with musicians however it can also used for other things.