This is the 13469th most frequent Russian word.
напишешь
"You will write."
In this sentence, 'напишешь' is used in the future tense, referring to the singular second person (you will write). It indicates an action that is expected to be completed.
Когда ты напишешь домашнее задание?
When will you write your homework?
Here, 'напишешь' is used in a conditional clause in the future tense, indicating an action that could occur depending on a condition.
Если напишешь книгу, она станет популярной.
If you write a book, it will become popular.
In this context, 'напишешь' refers to the second person singular future tense, indicating certainty about a planned action.