1. division into two classes.   fissure   dichotomy   cipher   anemia   Hint Half-n-half Clue   2. small planet.   conduit   effluvium   asteroid   atrophy   Half-n-half Clue   3. ability to produce desired effect.   component   atavism   chisel   efficacy   Half-n-half Clue   4. mode of formation or origin.   fissure   emetic   aperture   genesis   Half-n-half Clue   5. science dealing with sound.   acoustics   immobility   fauna   effluvium   Half-n-half Clue   6. substance formed by decay of organic material.   constraint   imbalance   humus   correlation   Half-n-half Clue   7. collarbone.   converse   clavicle   balm   fusion   Half-n-half Clue