【计】 loop-free directed graph
naught; nonexistence; not; nothing; without; lack; zero
【医】 a-; leipo-; lipo-; non-
cycle; recur; circle; rotate; circulation; repetition; revolution
【计】 DO-loop; for-loop; loop; unwinding
【化】 recirculate
【医】 circuIation; cycle
【经】 cycle; revolving; rotation
【计】 oriented graph