PARENTHETICALS are short stage directions referring to an action keyed to a specific line of dialogue, or the way that line is to be delivered ("Wry," "Angry," etc.). The rule of thumb is, Parentheticals are six words or less; if you have something longer to say, write it as Action text. Parentheticals tend to slow down the reading of the script, so try not to overuse them. Also, paretheticals should be adjectives, not adverbs-- meaning, you write "angry," not "angrily." Generally, if you have a word in a parenthetical that ends in "-ly"-- "sarcastically," "furtively," etc.-- it's probably wrong. They should start around 3½ inches from the left edge of the page. Do not confuse Parentheticals with Extensions.