Quartet.
A group of trees is called a wood from which a forest area could be called a woodland.
A group of five is called a "Quintet".
a small group
A quartet is a singing group of four.
Archipelago
Quartet or Foursome.
For Girl Guides of Thailand, the age group for ages 4 to 6 is called Littlebird while the age group for ages 7 to 11 is called Bluebird.
A quartet of muscians
a group of 4 sided shapes is called a quidrilatriel
Carbon is in group 14, (which is sometimes called group 4). Group 18 is the Noble gases (He, Ne, etc)
quadrumvirate