A lexeme is always a grammatical form, by definition. Lexemes are on the average larger than single morphemes but smaller than whole utterances. Many words are lexemes in many occurrences, and many lexemes are words. [...] But lexemes are in many cases smaller than what we usually call words [...].
- Hockett (1958), a pag.171

Many words are lexemes in many occurrences, and many lexemes are words. A minor deviation is that intonations count as lexemes: when speaking of words, or of minimum free forms, intonations have to be taken into account separately.
- Hockett (1958), a pag.171