prefix

Definition:

A letter or group of letters attached to the beginning of a word that partly indicates its meaning. Common prefixes include anti- (against), co- (with), mis- (wrong, bad), andtrans- (across).

Etymology:

From the Latin, "to fasten in front"

Examples & Observations:

§  circum = around
"Some circumstantial evidence is very strong, as when you find a trout in the milk."
(Henry David Thoreau)