English Words: U
23,789 words · Page 450 of 476
Any of several brownish-black forms of uranium dioxide, UO₂, (especially pitchblende) that is the chief ore of uranium; it is isomorphous with thorianite.
The element with atomic number 92 and symbol U. A radioactive silvery-grey metal in the actinide series.
A German project during World War II to research nuclear technology, including nuclear weapons and nuclear reactors.
A radioactive isotope of uranium, 23392U, having a half-life of about 160,000 years; it is fissile.
A fissile isotope of uranium, used for energy generation and in atomic weapons, containing 143 neutrons. It has a half-life of 7.038×10⁸ years; it decays into thorium-231 and ultimately lead.
An isometric-hexoctahedral mineral containing calcium, hydrogen, niobium, oxygen, tantalum, and uranium.
The actinocene cyclooctatetraenide with chemical formula U(C₈H₈)₂, one of the first organouranium compounds to be synthesized.
A tetragonal-ditetragonal dipyramidal mineral containing barium, hydrogen, oxygen, phosphorus, and uranium.
A rare yellow radioactive calcium uranium silicate hydrate mineral that forms from the oxidation of uranium-bearing minerals.
An orthorhombic-dipyramidal brown red mineral containing niobium, oxygen, tantalum, thorium, titanium, uranium, and yttrium.
An orthorhombic-disphenoidal yellowish white mineral containing oxygen, silicon, and uranium.
An orthorhombic-pyramidal mineral containing aluminum, fluorine, hydrogen, oxygen, phosphorus, and uranium.
An orthorhombic mineral containing barium, hydrogen, iron, lead, oxygen, tungsten, and uranium.
An isometric-hexoctahedral mineral containing calcium, cerium, fluorine, hydrogen, niobium, oxygen, tantalum, and uranium.
Of or relating to The Urantia Book, a spiritual and philosophical book of unknown authorship in the early 20th century.
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 450. 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.