solidus

noun pl. solidi

1. a gold coin of the Late Roman Empire
2. a medieval money of account worth twelve denarii: abbreviated s in £ s.d.
3. 1. a slant line (/), orig. the old long s (∫), used to separate shillings from pence (Ex.: 7/6)
   2. virgule

Origin: ME < LL < L solidus (nummus), lit., solid (coin)