Front

in-

Back

not or opposite

Examples: inconsiderate, ineligible

Front

ir-

Back

not or opposite

Examples: irregular, irrelevant

Front

dis-

Back

not or opposite

Examples: distrust, dislike

Front

il-

Back

not or opposite

Examples: illiterate, illegal

Front

un-

Back

not or opposite

Examples: unlock, unsafe

Front

mis-

Back

wrong, wrongly

Examples: misused, misinterpreted

Front

bi-

Back

two

Examples: bicycle, bipolar

Front

re-

Back

again or go back

Examples: reread, reheat

Front

mal-

Back

bad or no good

Examples: malpractice, malignant

Front

sub-

Back

under or below

Examples: submerged, subterranean