Difference between conversation and dialogue

[Veki]

Test No. incompl/inter-13 "At the Theatre", question 4

Many people go to the theatre not to see a play where the plot is complicated but to listen to the brillant ......... between the actors.

(a) dialogue
(b) chat
(c) conversation
(d) comments

Test No. incompl/inter-13 "At the Theatre", answer 4

Many people go to the theatre not to see a play where the plot is complicated but to listen to the brillant dialogue between the actors.

Correct answer: (a) dialogue

Your answer was: correct
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Please tell me what is wrong with "conversation" instead " dialogue"?
Do I have to use always dialogue in relation with "actors"?

[Alan]

Dialogue is a formal conversation typically in theatre or one that is prepared/written beforehand. Conversation is simply unprepared and casual.
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English as a Second Language
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