English Words: U
23,789 words · Page 17 of 476
Very fast, or of very short duration; especially concerning events that take place in femtosecond or picosecond timescales.
Filtration through a semipermeable membrane that only allows small molecules through.
A form of finitism that is even more extreme in that it denies those constructs whose construction cannot be physically performed (such as a number that no human could have time to calculate).
Having the properties exhibited by gases under very low pressures (one millionth of an atmosphere or less).
A generalization of a directed graph in which the source of an edge is a set of vertices rather than a single vertex.
Spelling & Dictionary Insight
The English alphabetical index for the letter U contains 23,789 headwords drawn from our Wiktionary-derived dictionary table. At 50 entries per page the browse splits into 476 pages, and you are currently viewing page 17. Every row above is a dictionary-backed entry with a canonical slug, and each links through to a full definition page with pronunciation, senses, etymology, and related-word data where available.
On this page 50 of 50 entries carry a part-of-speech tag and 50 carry at least one stored definition. Coverage varies across letters because Wiktionary volunteers build entries at different speeds for different parts of the alphabet, letters with common starting sounds (S, C, T, P) usually have the densest coverage, while less frequent starters (X, Q, Z) tend to have shorter but more specialised lists. PlainSpell surfaces whatever data is present and links back to the source when a definition is not yet recorded.
For readers using this index as a spelling reference, the guarantee is that every form you see on the list is a documented English headword, not a guess, not a derived inflection lacking a lemma row. If a word you expected to find is absent from the "U" list, it usually means the form exists only as an inflection of another lemma (e.g. a past participle stored under the infinitive) or the entry has not yet been imported from Wiktionary. Use the search bar or the misspelling lookup to resolve these cases.