The RULE 'I before E except after C, e.g.' is a common English language mnemonic used to remember the correct spelling of words that contain the letters 'ie' or 'ei'. This RULE states that when the letters 'ie' appear in a word, they should be pronounced as a long 'e' sound, unless the letter 'c' appears immediately before them, in which case they should be pronounced as two separate vowels. This RULE is not always followed, however, as there are many exceptions to it.