affix which is placed before the stem of a word

A prefix is a part of a word or a word, within a word. It is put at the start of another word to make a different meaning. It can also mean a number that is put in at the start to show which number something is in a group. It is a type of affix. compound nouns (in other cases also compound adjectives).

The following examples illustrate real prefixes.

Often people want to use a prefix to mean not. There are many prefixes that mean not.

  • Unnatural means not natural.
  • Apolitical means not political.
  • Nonviolent means not violent.
  • Indirect means not direct

We also learnt the prefixes anti which means against and auto is used to mean self or own

Some examples of these prefixes:

antisocial which means non social

anti glare which means it will prevent sun and light glare on a screen

autograph which means a person's signature

autopilot which means working by itself

Other examples of prefixes:

  • bicentennial (and other number related prefixes: mono, ter/tri, tetra, quadro, penta, hepta, octo, nano etc.)
  • contradiction
  • encompass
  • paratrooper
  • percent
  • periscope
  • prototype
  • polytechnical
  • react
  • semicolon

Scientists and doctors use prefixes in many words.

  • Hepato- is a prefix that means liver. So hepatocellular means 'about liver cells'.
  • Hydro- is a prefix that means water. So Hydroelectric dams are dams that make electricity from the flow of water.
  • Pre- or Ante- are prefixes that mean before. Prenatal diagnostics is the diagnostics done before the birth of a baby.
  • Post- is a prefix that means after. Post-traumatic experience would be an experience that was made after trauma.

Sometimes people make up words by adding a prefix. These words are not in a dictionary. But if people use these words enough, sometimes they go into dictionaries. For example, we can make the word unsimple, which splits up into not simple. This is not a word in a dictionary.

Compare to suffix. Suffixes are letters put at the end of a word to change its meaning.