Prematurely is from premature + -ly, from Latin praematurus ('ripe too soon'), from prae- ('before') + maturus ('ripe, mature'). Important recorded forms include praematurus (Latin) and maturus (Latin). Morphologically, the word preserves a built structure whose named elements carry the historical sense into English. The modern sense remains close to that composition, with the parts narrowing into a single lexical item. In current use it covers before the proper, usual, or expected time. The wider family includes related words such as premature, prematurity, and mature.