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unidad f. (Noun) "unity"

13th cent. From Latin unitatem, accusative of unitas 'id.' Derived from unus "one" (see uno).

Romance: Western Vulgar Latin: French unité, Italian unità
unir (Verb) "to join"

16th cent. From Late Latin unire 'id.,' a verb formed from Latin unus "one" (see uno).
universidad f. (Noun) "university"

Borrowed from Medieval Latin universitatem, accusative of universitas "university," but originally meaning "all things." From universus "all turned to one" (see universo).

Romance: Western Vulgar Latin: Asturian universidá, Portuguese universidade, Catalan universitat, French université, Italian università
universo m. (Noun) "universe"

Borrowed from Latin universum "all things turned in one;" "universe." From uni- "one" (see uni-) and versus "turn" (see verso).

Romance: Western Vulgar Latin: Portuguese universo, Catalan univers, French univers, Italian universo ; Eastern Vulgar Latin: Romanian univers
uno (Cardinal Number) "one"

10th cent. From Latin unus 'id.' Old Latin oino, accusative singular masculine of *oinos. From Proto-Italic *oino- 'id.' From late Proto-Indo-European *Hoi̯-no- 'id.' The first element *Hoi̯- is possibly from Proto-Indo-European *h1ei̯- "this/that."

Romance: Western Vulgar Latin: Asturian unu, Portuguese um, Galician un, Catalan un, French un, Italian uno ; Eastern Vulgar Latin: Aromanian un, Romanian unu ; Sardinian: unu

Indo-European: Celtic: Old Irish óen "," Middle Welsh un 'id.,' Old Breton un 'id.,' Cornish un 'id.;' Germanic: Gothic ains "one," Old Norse einn "," Old High German ein 'id.,' Old Saxon ēn 'id.,' Old English ān 'id.' (English one); Balto-Slavic: Serbian Chuch Slavic inъ "someone," Russian inój "other," Czech jiný 'id.,' Polish inny 'id.,' Slovene in 'id.,' Old Prussian ainan "one," Lithuanian víenas 'id.,' Latvian viêns 'id.;' Hellenic: Ancient Greek οἴνη (oíne) "one (one dice);" Indo-Iranian: Sanskrit éka- "one," Avestan aēuua- 'id.'
-ura Suffix forming abstract nouns from adjectives.

From Latin -ura 'id.' From the -u- in the past participle (e.g. pass-ere > pass-u-s) and suffix -ra, a descriptive noun-forming suffix from adjectives. Of unknown origin. It is possible the suffix is somehow from the feminine Proto-Italic adjective suffix *-rā (masc. *-ro-). In which case, it reflects Core Proto-Indo-European *-r-eh2, a feminine derivative of Proto-Indo-European *-ro-. Adding to the evidence are -t/s- extensions in Latin (-tura, sura), which is entirely expected of an internal derivation. But none of this answers the question of how a feminine adjective-forming suffix came to form abstract feminine nouns from adjectives. Also tempting is a borrowing, or semantic influence from the Etruscan suffix -ra, which did follow a path of forming adjectives and nouns.

Romance: Western Vulgar Latin: Asturian -ura, Portuguese -ura, Galician -ura, Italian -ura
usanza f. (Noun) "usage;" "custom"

Late 15th cent. From usar and -anza, a noun-forming suffix added to verbs indicating a condition.
usar (Verb) "to use"

Very early 13th cent. From Vulgar Latin *usare 'id.,' from Latin uti "to use" (Old Latin œti) and frequentive suffix -are (see note under faltar). From Proto-Italic *oit-e/o- 'id.' Probably from Proto-Indo-European *h3ei̯t- "to fetch," "to take along."

Italic: Paelignian oisa "used"

Indo-European: Hellenic: Ancient Greek οἴσω (oíso) "I bring;" Anatolian: Cuneiform Luwian hizzai- "to fetch"
uso m. (Noun) "use"

13th cent. From Latin usus 'id.' (Old Latin œsus). From the verb uti "to use" (see usar).

Romance: Western Vulgar Latin: Portuguese oso, Galician uso, French us, Italian uso
usted (Personal Pronoun) "you"

17th cent. Old Spanish vuasted, vuested, vusted. From vuestra merced (15th cent.). For a counter argument, however, see Menocal (1984), who argues an origin in Arabic ustad "professor."

In Latin America, usted is both formal and informal senses in the plural. In Spain, broadly speaking, usted is strictly formal.