In the context of dramatic text, "tone" is typically understood as the overall attitude of the text toward its subject matter or audience. It reflects the emotional quality or mood conveyed through the dialogue, stage directions, and the interactions between characters. Tone can be serious, comedic, sarcastic, formal, informal, etc., and it significantly impacts how the audience perceives the content and themes of the work.
The other options you mentioned—specifically, the direct and specific meaning of a word (denotation), the thoughts and associations a word invokes (connotation), and the way the plot is conveyed through words—relate to elements of language and literary analysis, but they do not define "tone" in the context of drama.