[...] the stem is the sound form on which a particular form is built.
- Aronoff (2004), a pag.60

I will adopt the traditional definition of a stem as the part of a complete word form that remains when an affix is removed.
- Aronoff (2004), a pag.49

Strictly speaking, stems are morphomic, because, as I have argued at some lenght, they are only sound forms of lexemes and not meaningful units.
- Aronoff (2004), a pag.72

While a lexeme has arbitrary properties on three dimensions - sound form, syntax, and meaning - as well as the usually arbitrary association among them, I will reserve the term "stem" for only the sound-form part of this trinity. A stem, in my use of this term, is a sound form. In particular, it is the phonological domain of a realization rule [...].
- Aronoff (2004), a pag.56