ETYM Old Eng. forti, fourti, fowerti, AS. feówertig; feówer four + suff. -tig ten; akin to OS. fiwartig, fiartig, Dutch veertig, German vierzig, Icel. fjörutîu, Swed. fyratio, Dan. fyrretyve, Goth. fidwôr tigjus. Related to Four, and Ten, Fourteen.
Being ten more than thirty; SYN. 40, xl, twoscore.

The cardinal number that is the product of ten and four; SYN. 40, XL.