Word Unit: ulula-, ululat- (Latin: howl, wail, screech, cry out)
Word Unit: -ulus, -olus, -ulum, -ola (Latin: suffix; little, small)
Word Unit: ulutat- (Latin: howl, screech, cry out)
Word Unit: -um (Greek > Latin: a suffix that forms singular nouns)
Word Unit: umbili-, umbil- (Latin: pertaining to the navel, umbilical cord; a protuberance or swelling; related to umbo, the boss [a convex elevation or knob] of a shield)
Word Unit: umbra-, umbro-, umbr-, umbel- (Latin: shade, shadow)

Other related "dark; shadow, shade; black" units: lygo-; melan-; nigri-; nocti-; nycti-; scoto-; skio-.

Word Unit: unci-, unc-, uncin- + (Greek > Latin: hook, hooked, bent, curved)
Word Unit: uncia- (Latin: inch; ounce; a twelfth)
Word Unit: -uncle + (Latin: a suffix; little, small)
Word Unit: -unculus + (Latin: a suffix; little, small)
Word Unit: undu-, und- (Latin > French: flow, wave, billow)

Inter-related cross references, directly or indirectly, involving word units meaning "more, plentiful, fullness, excessive, over flowing": copi-; exuber-; hyper-; multi-; opulen-; ple-; pleio-; plethor-; poly-; super-; total-; ultra-.

Word Unit: ungu- + (Latin: nail, claw, hoof)

A cross reference, directly or indirectly, involving a word unit meaning "nail (finger, toe); claw": onych-.

Word Unit: unguent-, unction- (Latin: ointment; anoint; smear)
Word Unit: uni-, un- (Latin: one, single; a word element for number 1)
Word Unit: -uous + (Latin: a suffix; tending to, inclined to)
Word Unit: upsilon; Υ, υ + (Greek: the twentieth letter of the Greek alphabet; Υ, υ; upsilon symbol with hook, ϒ)
Word Unit: uran-, urano- (Greek: heaven [s], vault of heaven; hence "the sky"; from Uranus, the god of the sky; in medicine, the palate, roof, or top of the mouth)
Word Unit: uranisc-, uranisco- + (Greek: roof of the mouth; literally, "little vault of heaven")
Word Unit: Uranus, words from myths (Uranus with Seventeen Sattelites; seventh planet from the sun)
Word Unit: urban- urb-, -urban, -urbia (Latin: city)