A particle s.l. is a word that does not inflect. This includes particles s.s. and, in many languages, adverbs, adpositions and conjunctions.

A particle s.s. is a particle s.l. which contracts no dependency relations. This excludes the other subtypes of the particle s.l. Since they contract no dependency relations, they do not project onto phrases. Nor are there productive patterns of the formation of particles.

The following classification of particles s.s. applies structural criteria at the highest levels and semantic criteria at lower levels. The categories of the lowest level are partly language-specific.

Classification of particles