optionally

Optionally, it can live up to its description by crashing into targets and detonating a five-pound warhead.

Regular university credit is given, but students may attend these lectures optionally and many do so.

In many cases, for this reason, good students take the subject optionally (without credit), though doing full work in it.

By the Egyptians it was practised in the same manner (excepting their Priests) as by the Tyrians,—viz., optionally.

At this time the sounds Hin and others may be made, alternately or optionally, according to habit.