[...] special clitics are really a kind of phrasal affix, that is, elements that encode properties of phrases in a way analogous to the way affixes record properties of words. [...] there could be two sorts of phrasal affix, corresponding to the difference between derivational and inflectional morphology. One set of special clitics (the derivational ones) would correspond to the introduction of changes in the semantic properties of the phrases they occurr in. These are the elements usually lumped together as particles, often quite obscure and discourse related, but not neutral in meaning. The other set (the inflectional ones) would then consist of auxiliares, tense markers, and clitic pronouns that represent the argument of the clause, or the corresponding elements like determiners and possessors within NPs.
- Anderson (2004), a pag.42