Prefixes help you understand unfamiliar vocabulary faster because they add meaning to the start of a word. A prefix can signal negation (un-), time (pre-), degree (over-), or position (sub-), making it easier to guess meaning in context.
List of Prefixes
A prefix is a group of letters added to the beginning of a word that changes the meaning of the base word.
| Meaning Group | Prefix | Core Meaning | Examples |
|---|---|---|---|
| Negation | un- | not; the opposite of | unhappy, unsafe, unfair |
| Negation | dis- | not; opposite; remove | disagree, dishonest, disappear |
| Negation | non- | not; without | nonfiction, nonverbal, nonstop |
| Negation | in- | not (common before some words) | inactive, incomplete, invisible |
| Negation | im- | not (before m/p/b) | impossible, impatient, imbalance |
| Negation | il- | not (before l) | illegal, illogical, illegible |
| Negation | ir- | not (before r) | irregular, irresponsible, irrelevant |
| Time / Order | pre- | before | preview, pretest, prewar |
| Time / Order | post- | after | postgraduate, postnatal, postgame |
| Time / Order | fore- | before; in advance | forecast, foreshadow, foresight |
| Time / Order | mid- | middle | midterm, midnight, midway |
| Time / Order | ex- | former | ex-president, ex-wife, ex-manager |
| Repetition / Return | re- | again; back | rewrite, rebuild, reconnect |
| Error / Badly | mis- | wrong; badly | misjudge, misunderstand, misplace |
| Position / Location | sub- | under; below | submarine, subway, substandard |
| Position / Location | inter- | between; among | international, interstate, intermission |
| Position / Location | trans- | across; through | transfer, transport, transatlantic |
| Degree / Size | over- | too much; excessively | overload, overwork, overcook |
| Degree / Size | super- | above; beyond | superstar, supersonic, superhuman |
| Degree / Size | semi- | half; partly | semicircle, semifinal, semiannual |
| Self | auto- | self | automatic, autograph, autopilot |
| Opposition | anti- | against | antidote, antisocial, antivirus |
Prefixes in Science
In science, prefixes often help describe concepts more precisely.
Bio-
Bio- relates to life. Examples: biome, biopsy, biosphere.
Geo-
Geo- relates to the Earth. Examples: geography, geology, geothermal.
Astro-
Astro- relates to space. Examples: astronomy, astronaut.
Prefixes in Mathematics
In mathematics, some prefixes describe number or quantity.
Mono-
Mono- means one. Example: monomial.
Poly-
Poly- means many. Example: polygon.
Deca-
Deca- means ten. Example: decagon.
Prefixes are also used in the metric system:
| Prefix | Symbol | Meaning |
|---|---|---|
| kilo- | k | thousand |
| hecto- | h | hundred |
| deka- | da | ten |
| deci- | d | tenth |
| centi- | c | hundredth |
| milli- | m | thousandth |
Prefixes in Medicine
In medical terms, prefixes often describe level, position, or condition.
Hypo-
Hypo- means “under” or “below.” Example: hypoglycemia (low blood sugar).
Hyper-
Hyper- means “over” or “above.” Example: hyperglycemia (high blood sugar).
Epi-
Epi- means “on” or “upon.” Example: epidermis.
Last Updated on January 21, 2026
- Accept vs. Except: The Simple Difference (with Rules) - January 14, 2026
- Averse vs. Adverse: Simple Rules to Master These Confusing Words - January 14, 2026
- Advice vs. Advise: How to Use Them Correctly - January 14, 2026
