Learn Spanish (Latin America): Di tu línea con mucha emoción.

Di is the irregular informal command (the affirmative tú imperative) for the verb decir (to say or tell). When you are telling a friend or someone you are on a first-name basis with to say something, you must memorize and use this special short form.

Why doesn't tu have an accent mark in this sentence?

Without the accent mark, tu is a possessive adjective meaning "your" as in tu línea. With the accent mark, tú is the pronoun meaning "you". Since the sentence is talking about "your" line, we use the version without the accent mark.

Does línea mean an actor's line in a script?

Yes! Just like in English, línea can mean a physical line drawn on paper, but it is also commonly used to refer to a line of dialogue that an actor says in a play, movie, or show.

Why is it mucha instead of mucho here?

The word mucha describes emoción. In Spanish, almost all nouns ending in -ción are feminine. Because emoción is a feminine noun, you must use the feminine form mucha to match it.