These ROOT-WORDS are OPUS & OPER meaning WORK. They come from the Latin words OPUS & OPERA (plural). While the original meaning is closest to the Latin word No. 19 and the plural is in use mostly as a singular word meaning No. 1 (plural is operas), this root has become a word for any work which is planned, acted on, and carried through. So we OPERate and have OPERations, and everything seems to be moving in an OPERational manner, with OPERators and coOPERators.
1. Opera : OPER a (op’ e ra) n.
A drama which has been set to music and is sung instead of spoken
2. Operatic : OPER atic (op e rat’ ik) adj.
Resembling an opera; having qualities of opera
3. Operable : OPER able (op’ e ra b’l) adj.
Can be treated by an operation
4. Operameter : OPER ammeter (op er am’ e ter) n.
An instrument for counting the rotations of a wheel in a machine
5. Operalogue : OPER alogue (op’ er a log) n.
A lecture on opera which presents a summary of the story