Lexical units

upright=1.5|thumb|Sign of a New Zealand hill with an unusually long one-word name: [[Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu| (85 characters)]]

An idiom is a phrase or expression that largely or exclusively carries a figurative or non-literal meaning, rather than making any literal sense. Categorized as formulaic language, an idiomatic expression's meaning is different from the literal meanings of each word inside it.

thumb|upright=1.3|A comparison of prepositions and directional prefixes in Greek, Latin, English, and German.

In linguistics, an affix is a morpheme that is attached to a word stem to form a new word or word form. The main two categories are derivational and inflectional affixes. Derivational affixes, such as un-, -ation, anti-, pre- etc., introduce a semantic change to the word they are attached to. Inflectional affixes introduce a syntactic change, such as singular into plural (e.g. -(e)s), or present simple tense into present continuous or past tense by adding -ing, -ed to an English word. All of them are bound morphemes by definition; prefixes and suffixes may be separable affixes.

indivisible part of word that does not have any affix, may have a meaning and be usable alone or not, and may comprise multiple "radical" forms

A lexeme () is a unit of lexical meaning that underlies a set of words that are related through inflection. It is a basic abstract unit of meaning, a unit of morphological analysis in linguistics that roughly corresponds to a set of forms taken by a single root word. For example, in the English language, run, runs, ran and running are forms of the same lexeme, which can be represented as RUN.

canonical representation of a lexeme

In corpus linguistics, a collocation is a series of words or terms that co-occur more often than would be expected by chance. In phraseology, a collocation is a type of compositional phraseme, meaning that it can be understood from the words that make it up. This contrasts with an idiom, where the meaning of the whole cannot be inferred from its parts, and may be completely unrelated.

basic unit of a language’s lexicon

concept in English grammar