In English, of the letter sequences "ie" and "ei" occurring in spellings of words, "ei" is rare except when used after "c" to form "cei"; furthermore, letter sequence "cie" is rare (it occurs mostly in the plural of nouns ending "-cy" such as efficiency). This general rule is commonly known as the I before E except after C rule (see category). The rule has several variations and exceptions, including when the "ei" makes the long "a" sound such as in neighbour, weigh, beige and rein.

Listed below are some words which are exceptions to the most basic rule of "I before E except after C". Note that this list is incomplete and also does not include all variations of each word (such as theirs or sciences).

Specifically, words that break the rule either: