What is the meaning of U-?

Alternative form of μ- as an abbreviation of micro-, mikro-, микро- etc.

Combining form of ur (“water”)

I

you singular (used for conjugating verbs to the subjective or nominative case of the personal pronoun)

Alternative form of mu-

you, thou; second-person singular subject concord.

Class 1a noun prefix.

he, she, it; class 1 subject concord.

he, she, it; class 3 subject concord.

Class 11 noun prefix; form of ulu- used before stems of more than one syllable.

un-, im-

an abbreviation of certain words beginning with "u"

un- (not)

used to create an undesired version of the following noun

used to strengthen/intensify the following noun

an abbreviation of certain words beginning with "u"

perfective prefix

you, thou; second-person singular subject concord.

he, she, it; class 1 subject concord.

he, she, it; class 3 subject concord.

Forms perfective verbs with the following meanings:

1. (no change in meaning)

   (no change in meaning)

   away

   to make a mistake while

   you, thou; second-person singular subject concord.

   he, she, it; class 1 subject concord.

   he, she, it; class 3 subject concord.

   you, thou; second-person singular subject concord.

   he, she, it; class 1 subject concord.

   he, she, it; class 3 subject concord.

   Third person singular subject + third person duoplural object.

   Marks the irrealis mood

   Allomorph of y- (first-person prefix) used for stems that begin with two consonants and have a first vowel u.

   With following vowel lengthened if in an unreduced open syllable.

   (away) from

   (inchoative)

   (telicity)

   added to mean a bit

   (u- + imperfective base + se) intensification: until exhaustion, expressing final stage of a process. (collocates with k smrti (“to death”))

   (on perfective verbs) unintentionally, inadvertently, by mistake

   (root modality) [i.e., deontic + dynamic modality: ability, obligation, permission, readiness]

   to gain by activity

   in-, un-, non-; (prefix meaning not, reversing the meaning)

   appears in front of some verbs meaning: to make something behave in a certain way, en-, be-, make

   perfective prefix

   added to mean "a bit"

   added to mean away

   added to mean successfully, often without an imperfective counterpart

   u class_(XI) noun prefix, denoting natural objects, extensions, abstract qualities, or collections of small things.

   -ness, -ity

   forms names of countries

   you, 2nd person singular subject concord

   it, m class_(III)/u class_(XI) subject concord

   verb-initial form of -u- (“it, m class_(III)/u class_(XI) object concord”)

   you, thou; second-person singular subject concord.

   Class 1a noun prefix.

   he, she, it; class 1 subject concord.

   he, she, it; class 3 subject concord.

   Class 11 noun prefix; form of ulu- used before stems of more than one syllable.

   abstract or instrument nominalizing prefix

   non-gerundive nominalizing prefix

   you, thou; second-person singular subject concord.

   Class 1a noun prefix.

   he, she, it; class 1 subject concord.

   he, she, it; class 3 subject concord.

   Class 11 noun prefix.

   Source: wiktionary.org