This document outlines a lecture on lexical semantics and multilingualism. It discusses the differences between linguistic ontologies and application ontologies. It introduces key concepts in lexical semantics like the semantic triangle, polysemy, and synonymy. The semantic triangle illustrates the indirect relationship between symbols, concepts, and things in the real world. Polysemy refers to a word having multiple meanings, while synonymy refers to different words having the same meaning. The document also discusses how concepts are shared to varying degrees across languages, with more interaction between language communities leading to more shared concepts.