“The difference between the right word and the almost right word is the difference between lightning and a lightning bug.” ― Mark Twain. Words can have more than one basic meaning and some words sound similar but have a completely different denotation. For example:    (Wrong) Older people often suffer infirmaries . (a place for the sick)    (Right) Older people often suffer infirmities. (disabilities) Some words are homonyms (sound-alikes) but mean very different things. For example, principal/principle or rain/reign/rein.  Then there are words with similar but distinct meanings.    (Wrong) Television commercials continuously (unceasingly) interrupt programming.    (Right) Television commercials continually (regularly) interrupt programming. Which vs That.  "Which" is used to introduce non-restrictive clauses (extra but not essential information) such as in The leftover lettuce, which is in the refrigerator, would make a ...