The PARTOF relation is the fundamental syntactic or combinatorial relation. Like ISA, the term is also rather general, and a wide range of different relations are covered by it in different approaches to linguistics in general and lexicography in particular: syntagmatic relations, mereological (merological) / mereonomic (meronomic) relations, part-whole relations, part-part relations, (immediate) constituency / domination, command relations (e.g. c-command), dependency relations, government relations, argument structure, thematic role structure, subcategorisation frames, case frames, valency, anaphoric binding relations, categorial functor-argument application, concatenation, linear ordering, prosodic (autosegmental) association and precedence relations, child-child (sister) relations, parent-child (mother-daughter) relations.
Modern theories of grammar are largely lexicalist, that is, combinatorial PARTOF properties are assigned to lexical items rather than being formulated as an autonomous grammar module in language descriptions. Lexical properties such as argument structure, and others listed above, are perhaps the most intensively treated topic in current lexicography, particularly in the semantic sub-domains.