n.1 the act or an instance of forming; the process of being formed.
2 a thing formed.
3 a structure or arrangement of parts.
4 a particular arrangement, e.g. of troops, aircraft in flight, etc.
5 Geol. an assemblage of rocks or series of strata having some common characteristic.
Derivatives:
formational adj.
Etymology: ME f. OF formation or L formatio (as FORM)