One-parameter Group

In mathematics, a one-parameter group or one-parameter subgroup usually means a continuous group homomorphism

φ : R → G

from the real line R (as an additive group) to some other topological group G. That means that it is not in fact a group, strictly speaking; if φ is injective then φ(R), the image, will be a subgroup of G that is isomorphic to R as additive group.