take the opportunity to do something else; while you're at it
Used when doing something additional or different while already engaged in another activity. Often appears in the pattern ～のついでに.
See also: もののついで
If you're going shopping, stop by the post office while you're at it.
I took the opportunity to wipe the windows too.
Kanji spelling; rarely used in practice.
Kanji spelling with 序で; rarely used in practice.
From 事 (こと, 'thing, matter') + の (possessive particle) + 序で (ついで, 'order, opportunity'). The exact historical derivation is uncertain, but the phrase has been used since at least the Edo period to mean 'taking the opportunity of something'.