[...] under all the permutations certain pairs or triples of morphemes will behave as "blocks", not only occurring always together, but also in the same order relative to one another. [...] One of the characteristic of the word is that it tends to be internally stable (in terms of the order of the component morphemes), but positionally mobile (permutable with other words in the same sentence).
- Lyons (2004), Pag. 21