The quality or state of being firm; steadfastness, solidity, and unwavering determination.
From Latin firmus (firm) + -tude (a suffix from Latin -tudo denoting quality or state, as in 'magnitude' and 'altitude'). Emerged in Middle English as a philosophical term.
Unlike 'firmness' which is everyday language, 'firmitude' sounds like you're giving a philosophy lecture—it's a Latinate way of discussing firmness as an abstract moral virtue.
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