prefix

A prefix is an affix attached to the front of a word to modify its meaning or grammatical function. In linguistics, prefixes are bound morphemes that precede a word’s base and are used to form new words or alter their role in a sentence.

Origins and types: Prefixes can be derivational, creating new words or changing part of speech (for example, un- in unhappy, re- in rewrite, pre- in preview). They can also be inflectional, signaling grammatical information, though in English most inflection is carried by suffixes rather than prefixes. Some languages use prefixes extensively to mark tense, number, or case. The same prefix may have multiple meanings and can be productive (generating many new words) or limited to historical forms.

Orthography and phonology: Prefixes may be written as a single word or with a hyphen in certain compounds, depending on readability and style guides. Phonological effects vary: some prefixes cause minor changes in pronunciation through assimilation, while others remain largely phonologically transparent.

Other domains: The term prefix also appears outside word formation. In science, SI prefixes such as kilo-, centi-, and milli denote powers of ten. In mathematics and computer science, prefix notation places operators before operands, as in Polish notation, and is used in some programming languages and calculators.

Etymology and cross-linguistic use: Many prefixes derive from Latin or Greek roots and have spread across languages with related meanings. Prefixes interact with roots to shape semantics and syntax, and their use can reflect historical sound changes and language contact.

See also: affix, morpheme, suffix, infix, circumfix.