Not enough in amount or quality; not good enough for a particular purpose.
From Latin 'in-' (not) and 'adaequatus' (made equal to), from 'ad-' (to) and 'aequus' (equal). It literally means 'not made equal to the need'.
If something is inadequate, it doesn’t ‘measure up’ to what’s required. The emotional sting of the word comes from that idea of not being equal to the task or standard.
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