13/6/17 The Meaning of Bi and Semi

The Meaning of Bi and Semi

Bi- means “two” <bicycle> <bifocal> <bilateral>.
Semi- means “somewhat” and, specifically, “half” <semicircle> <semifinals> <semisweet>.

But the literal meanings have been abused in practice when used as periodic prefixes: biannual has come to be synonymous with semiannual, meaning twice a year (biennial means every other year), and biweekly newspapers publish twice a week. To avoid confusion, spell it out to your reader <the board meets every other week>.