 Possibly because of lack of clarity affecting the notion of sense, and surely because of Russell’s (1905) authoritative criticism of Fregean semantics, word meaning disappeared from the philosophical scene during the 1920s and 1930s. In Wittgenstein’s Tractatus the “real” lexical units, i.e., the constituents of a completely analyzed sentence, are just names, whose semantic properties are exhausted by their reference. In Tarski’s (1933) work on formal languages, which was taken as definitional of the very field of semantics for some time, lexical units are semantically categorized into different classes (individual constants, predicative constants, functional constants) depending on the logical type of their reference, i.e., according to whether they designate individuals in a domain of interpretation, classes of individuals (or of n-tuples of individuals), or functions defined over the domain. However, Tarski made no attempt nor felt any need to represent semantic differences among expressions belonging to the same logical type (e.g., between one-place predicates such as ‘dog’ and ‘run’, or between two-place predicates such as ‘love’ and ‘left of’). See the entry on  Alfred Tarski.