Not having great significance, value, or influence; trivial or minor.
From prefix 'un-' (not) plus 'important' (from Latin 'importare,' to matter/be significant). The word is a straightforward negation formed in English.
The word 'unimportant' is interesting because it's rarely what we really mean—we usually say 'trivial,' 'minor,' or 'insignificant' instead, suggesting that English speakers feel 'unimportant' sounds awkwardly wishy-washy compared to stronger negatives.
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