Realizational morphology or "word-and-paradigm" (WP) was a theory first created by linguist Charles F.
Instead, inflections are stem modifications which serve as exponents of morphological feature sets.
The examples are usually drawn from fusional languages, where a given "piece" of a word, which a morpheme-based theory would call an inflectional morpheme, corresponds to a combination of grammatical categories, for example, "third person plural".
[4] Morpheme-based theories analyze such cases by associating a single morpheme with two categories.
Item-and-Process theories, on the other hand, often break down in cases like these, because they all too often assume that there will be two separate rules here, one for third person, and the other for plural, but the distinction between them turns out to be artificial.