Several linguists have argued that one should distinguish between the "actual lexicon", the collection of all actual, or item-familiar [...] words, and the "potential lexicon", consisting of all potential, or type-familiar, words. Naturally, the actual is always part of the potential, so the actual lexicon is a substructure of the potential lexicon.
- Hoeksma (2004), Pag. 186

The set of all actual words is the actual lexicon. The actual lexicon is by definition a subset of the potential lexicon, since each actual word can be derived from an actual word in zero step.
- Hoeksma (2004), Pag. 187