Semantics: the meaning of words and the meaningful roles of words in phrases or sentence contexts. The definitional meanings of words, including the semantic features of the word "ball" (such as "round," "can be thrown," etc.), the referent categories of words (such as "baseball," "football," "soccer ball," etc.) as well as the meaningful roles (semantic relations, function, or thematic roles such as Agent or Performer of Action) are all part of semantics.