The productiveness or non-productiveness of a formation is similarly a meaningful morphemic feature. As descriptive linguists we are sometimes inclined to overlook such a dynamic aspect of the language. We assume that a form is a fixed feature and that its distribution is fully defined or definible. We tend to imply that productiveness is only a diachronic fact, but it may be a synchronic reality as well.
- Nida (1948), a pag.431

Any body of material sufficiently extensive to serve adequately as a basis for descriptive analysis must include fluctuations of forms, which are symptomatic of different degrees of acceptability. Synchronic contrasts of this kind are closely allied to contrasts of productivity vs. non-productivity.
- Nida (1948), a pag.431