In a manner that is not needed or required; without necessity or good reason.
Formed from 'un-' (not) + 'necessary' (from Latin 'necessarius' meaning unavoidable) + '-ly' (adverbial suffix). The word 'necessary' comes from 'necesse' meaning 'not able to give way', literally 'not yielding'.
This word perfectly embodies the concept of linguistic economy—ironically, it's often unnecessarily long for what it expresses! Many style guides suggest replacing it with simpler alternatives like 'needlessly' or restructuring sentences to avoid it entirely.
Complete word intelligence in one call. Free tier — 50 lookups/day.