This lecture discusses the concepts of polysemy and homonymy as linguistic phenomena. It covers the meaning and polysemy of words, the semantic structure of words, the notion of lexico-semantic variants, homonymy of words and word-forms, sources of homonymy, and the classification of homonyms. It also explains that while monosemantic words with only one meaning are limited in English, the majority of words are polysemantic with multiple meanings.