1. friction   attrition by rubbing or disagreement.   exhalation affecting smell.   parallelism or similarity.   halo or circle of light.   Hint Half-n-half Clue   2. acoustics   machine to separate substances by spinning.   swirling motion of water or air.   science dealing with sound.   defect in eye or lens preventing proper focusing.   Half-n-half Clue   3. cistern   reservoir or tank for water.   loss of speech.   swirling motion of water or air.   tree bearing fruit-cones.   Half-n-half Clue   4. dichotomy   narrow opening or crevice.   tree bearing fruit-cones.   conjecture or logical projection beyond range.   division into two classes.   Half-n-half Clue   5. effervescence   giving off of gas bubbles or exuberance.   spread of disease by contact.   masses of leaves or leafage.   working of the brain or thought.   Half-n-half Clue   6. fusion   botanical garden where trees are studied and exhibited.   united mass or coalition.   small pricking tool for piercing holes.   disproportion or lack of balance.   Half-n-half Clue   7. component   constituent or element.   ability of system to maintain stability.   substance producing condition of no sensation.   point on which lever is supported.   Half-n-half Clue