Prefix · quantity · one
Means "one" or "single": uniform, unique, universe, unity, unicorn, unify.
Written by Bryan López, English teacher · Updated
Uni- comes from Latin "unus" (one) and signals oneness or singularity. It appears in words describing a single unit, a single form, or the act of becoming one: uniform = one standardised form; unique = one of its kind; universe = everything turning as one; unify = to bring many into one; unity = the state of being one.
Both uni- (Latin) and mono- (Greek) mean "one," but they are not interchangeable. Uni- prefers formal and everyday vocabulary with Latin roots: uniform, unique, union, universal. Mono- prefers scientific and technical vocabulary with Greek roots: monologue, monopoly, monotone, monochrome. The historical root of the word determines which prefix it takes.
Attaches to nouns and adjectives to mean "one" or "single":
Pronunciation: /juːnɪ/. Spanish cognates: uniform/uniforme, unique/único, universe/universo, unity/unidad, unicorn/unicornio, unify/unificar — all direct equivalents. Do not confuse with mono- (Greek origin, more scientific): unicycle vs. monorail.
uni-/juːnɪ/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
"Uni-" and "mono-" both mean "one" but are not freely interchangeable. "Uniform" is not "monoform." "Monologue" is not "unilogue." The historical root of the word determines the prefix: words of Latin origin take uni-; words of Greek origin take mono-. When in doubt, uni- is the safe choice for everyday words.
A trick to remember it
Uni- = one. Spanish speakers have a huge advantage: uniform/uniforme, universe/universo, unity/unidad, unique/único, unicorn/unicornio are all exact cognates. Every time you see "uni-" in English, you already know what it means.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What is the difference between "uni-" and "mono-"?
The prefix uni- means "one" or "single": uniform, unique, universe, unity, unicorn, unify. In Spanish it usually maps to uni-.
The prefix uni- is pronounced /juːnɪ/. For example, "uniform".
"form" becomes "uniform". It is a typical example of the uni- prefix.
Signals two or double: bicycle, bilingual, bilateral, bifocal, biannual.
Signals one or uniqueness: monologue, monopoly, monotone, monochrome, monolingual.
Signals many or multiple: multiply, multicultural, multimedia, multitask, multilingual.
Signals three: triangle, trilogy, tricycle, triathlon, tripod, trimester.
un-, re-, pre-, dis-, over-, in-... every beginning you need to unlock thousands of English words at once.