quantity is properly applied to that which is measurable, as is "number" to that which may be counted. "A quantity of people"; "a quantity of birds," are both incorrect; substitute the word number in both cases.
quarter of: As applied to time this is incorrect. Such an ambiguity can be avoided by substituting to for of. For example, a quarter of seven is one and three-fourths not a quarter to the hour of seven; yet the phrase "quarter of" is often misapplied to time by persons of average education.
quit is sometimes used incorrectly for cease. You may quit business, but do not ask your companion to "quit fooling."
quite: In general quite means "to the fullest extent, totally, perfectly"; colloquially, it means "very, considerably." It is from the French quitte, meaning "discharged," being the equivalent of the Enghsh "quits," a word used in games to designate when the players are even with one another. Therefore such a phrase as "quite a number" is unjustifiable. "Number"' is indefinite in its significance just as are also "few," "little," and "some." As Richard Grant White says, "A cup or a theater may be quite full; and there may be quite a pint in a cup or quite a thousand people in the theater; and neither may be