Definition of "lexical"

So, it seems clear that the idiosyncratic restrictions relating to the range of complements which a Preposition does or does not permit are directly analo- gous to the parallel restrictions which hold in the case of Verbs. The restric-tions concerned are not categorial in nature (i.e. they are not associated with every single item belonging to a given category): on the contrary, they are lexical in nature (that is to say, they are properties of individual lexical items, so that different words belonging to the same category permit a different range of complements).

1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 137