The notion lexical item is used to cover any lexical sign type but also other inventorisable items such as affixes and phonemes, whose lexical status in linguistics is controversial. Some examples of structural semiotic characterisations of these items are given below.
Phoneme: A minimal sign with no MEAN specification and no PARTS (pace proponents of distinctive features and autosegmental lattices; sub-morphemic morphological composition is not at issue here).
Morpheme: A sign with elementary MEAN specification, the PHON of whose PARTS is specified for a concatenation of phonemes.
Lexical morpheme, lexical base, root: A simple stem; a grammatical morpheme is an affix.
Cranberry morph: A morpheme with no specification for MEAN.
Word: A word (in English) is specified recursively for all four structural semiotic properties:
Stem: A lexical root, or an item to which an affix is attached to form a derivation or an inflection, or to which a word or another stem is attached to form a compound word.
Derivation: A complex stem consisting of a single root attached to an affix; the type affix covers prefixes, suffixes, infixes, interfixes, introfixes (intercalations), superfixes, and `attached to' covers the relevant compositional part-part operations.
Compound: A complex stem consisting of more than one root, each of which may be the centre of a derivation and may be inflected; a compound word must terminate in an inflected root or an inflected derivational suffix.
Phrasal idiom: A lexical sign licensed by the principles and rules of sentence structure, with some PARTS unspecified according to the frozenness hierarchy of idiomaticity.
Lexical prosody: A superfix item with semiotic properties like those of phonemes or morphemes, but which is not concatenated but prosodically associated with other phonemes or morphemes. Prosodic association is interpreted as temporal overlap () of phonetic events, while concatenation is interpreted as immediate precedence ( ) of temporal events [Carson-Berndsen 1993]. A more general relation of precedence ( Y) is often used.
Nonce word: A sign licensed by the word constraints, but not inventarised as a lexical sign.
Phrase, sentence: A sign licensed by the phrasal idiom constraints, but not inventarised as a lexical sign.
In the view represented by the ILEX model, all sign types are grounded in lexical signs of the corresponding ranks. Morphology is thus seen as the discipline dealing with generalisations over lexicalised words, syntax in the traditional sense of the term is seen as the discipline dealing with generalisations over phrasal idioms, and so on.