a combining form borrowed from Latin, meaning "half," freely prefixed to English words of any origin, now sometimes with the senses "partially," "incompletely," "somewhat": semiautomatic; semidetached; semimonthly; semisophisticated.
[ ME semi-; c. OE som-, sam- half (mod. dial. sam- ), OHG sami-, Skt sami-, Gk hemi-; cf. SESQUI- ]
Usage . See bi- 1 .