undo

Spelling & Dictionary Insight

The English entry for undo is 4 letters long, classified as averb, and transcribed in the International Phonetic Alphabet as /ʌnˈduː/. Corpus data places it at rank #13,631 in overall English word frequency, marking it as uncommon enough that many writers pause before typing it.Wiktionary records 4 distinct senses for this headword, so context determines which meaning a reader should apply.

Our Hunspell-derived misspelling index lists 5 documented wrong-spelling variants for undo, with forms such as "nudo", "udno", and "unddo". Each variant represents a distinct typo pattern that appears often enough in corpora to be worth flagging, typically a doubled-consonant error, a silent-letter drop, or a vowel substitution.It also participates in 20 confusable-pair relationships, "UO", "USD", "uni", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: From Middle English undōn, from Old English ondōn, from Proto-West Germanic *andadōn (“to undo”), equivalent to un- + do. Cognate with West Frisian ûndwaan, ûntdwaan (“to undo; rid”), Dutch ontdoen (“to undo”). Root origin matters for spelling because borrowed morphemes (Greek, Latin, Old French, Old English) carry their source-language orthographic conventions into modern English, which is why historical etymology is often the cleanest predictor of whether a cluster like "-ough", "-eau", or "-tion" will appear. For readers arriving here from a spelling check, the authoritative guidance is: the correct English form is undo, spelled U-N-D-O, and any other sequence of those letters, regardless of how natural it feels, is a misspelling in standard orthography.