The word пока is a conjunction that means “while.” It can be used with verbs in the past, present, or future:

When пока means “while,” it is essentially synonomous with когда followed by an imperfective verb, although sometimes the пока version sounds a bit better than the когда version, and sometimes it's the other way around. But on the whole all three of the sentences we just saw can be rewritten with когда and mean essentially the same thing:

• Папа готовил ужин, когда мама убирала в гостиной.
• Каждое утро, когда я одеваюсь, брат принимает душ.
• Когда я буду в Москве, я буду ходить на занятия йоги два-три раза в неделю.

In grammatical terms the clause that contains пока is called a subjoined clause. The other clause is called a main clause. A subjoined clause that begins with пока in the “while” meaning must always contain an imperfective verb as its primary verb. The main clause can have either a perfective verb or an imperfective verb.

The verb in the main clause simply follows the standard rules for the imperfective/perfective distinction.

What we've written here probably seems way too basic to warrant a blog entry. So why bother? There's a method to this madness. Tomorrow's entry discuss the word пока when it combines with the negative particle не, and that combination often throws people for a loop. You may want to refer back to this entry once you've read the next one to see the contrast.