when it is the "tu" form, when is it with the "s" ending and when is it without?
For verbs ending in -er, you dont use the s ending, except when followed by y and en. Instead use mange, parle, etc for tu. For verbs ending in -ir and re, you treat these normally, e.g. "choisis" and "fais"
The second person doesn't always take an S in the imperative, but it does in the present tense, except for a few verbs that end in X.
His question was when the 2nd person singular of the imperative preserves the S of the present conjugation.
We often use 'speak' in this phrase. Do the French?
"Parler" = to speak, to talk. It's the same. Use the more natural English word.
question- why is the tu form of etre correct in Ne sois pas triste, but incorrect in Ne me parle pas? (sorry, my alt + is on the blink)
There is an exception for -er verbs which you can read about in the notes before the lesson now :) So its parle, laisse, mange for tu form using imperative in most cases