Let us assume that LF must be so designed that such expressions as "the man, John, he" are assigned θ-roles, that is, are assigned the status of terms in a thematic relation. Let us call such expressions "argument", as distinct from idiom chunks (e.g. "too much" in "too much has been made of this problem") [...] Thus, we understand NP arguments to be NPs with some sort of "referential function", including names, variables, anaphors, pronouns.
- Chomsky (1993), Pag. 35

Let us now assume that arguments fall into the following categories: (1) (i) overt anaphors (ii) pronominals (iii) R-expressions (iv) clauses [...] The intuitive idea is that arguments are the elements that bear a θ-role. Thus each argument or its trace is in a θ-position, hence an A-position.
- Chomsky (1993), Pag. 101

Note that the term "argument" is often used differently in linguistic work, referring to elements occupying "argument positions", the latter being base-generated NP positions.
- Chomsky (1993), Pag. 138