Usually said in a situation when the rule is incorrect and unusable.

plural of first-chance exception

The rare occurrence of a counterexample to a rule, used to demonstrate that the rule exists.

(grammar) A phenomenon where the subject of an embedded infinitival verb seems to appear in the superordinate clause, and, if a pronoun, is unexpectedly marked with objective case morphology.

(idiomatic) These negative remarks do not pertain to anyone who is currently listening to them (including the speaker).

plural of exception that proves the rule

plural of exception that proves the rule

(orthography, mnemonic) In English words that contain the letters I and E together, the I tends to come before the E (ie), except in cases when the two are preceded by the letter C, in which case the E comes before the I (cei).

Alternative letter-case form of I before E, except after C

Alternative form of there is an exception to every rule