[...] affixes are formal representations of lexical and syntactic grammar; they therefore belong to the closed classes of grammar and have no meaning at all except in the context of the lexemes whose syntactic and lexical relations they mark.
- Beard (2004), Pag. 508

Affixes in a class with stems is a variant of the structuralist concept of the morpheme, an isomorphic association of mutually implied sound and meaning.
- Beard (2004), Pag. 468

Lieber [Lieber Rochelle 1981a, “On the organization of the Lexicon”, Indiana University Linguistics Club, Bloomington, Indiana] has developed that position into a complete theory which I will call the Lexical Morphology Hypothesis (LMH) since it locates lexical (L-) and inflectional morphology in the lexicon. Such a site for morphology implies that affixes are some type of sign like lexemes, such that affixation may be accomplished by rules of compounding.
- Beard (2004), Pag. 468