Buying qat* qua† tobacco in the suq‡ is bad qi**.
*qat - A type of plant which behaves as a stimulant when chewed or brewed. Also spelled "khat," "kat," etc.
†qua - Latin for "in the capacity of"
‡suq - A bazaar or commercial district in the Arabic world. Also spelled "souq," "souk," etc.
**qi - In Chinese philosophy, the underlying life force in all things, believed to cause bad health if not properly balanced. Apparently the plural is "qis," although I don't see how a non-count noun can have a plural. Also spelled "chi," "ch'i," etc.
(This entry was brought to you by the letter Q, which is worth 10 points in Scrabble.)