A French title of respect for a man, equivalent to 'Mr.' or 'Sir' in English.
From Old French 'mon seigneur' (my lord), contracted into one word by the 1600s, it mirrors the evolution of Spanish 'señor' from 'señ or' (my lord).
Monsieur is literally 'my lord' compressed into a single word—and similar compressions happened in every Romance language, showing how respectful titles naturally evolve from full phrases into single words.
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