в тече́ние vs за

v techenie vs za — during/within a period vs in time needed to complete

What it really means

В тече́ние means “during” or “throughout a period” and normally takes the genitive: в течение недели, “during the week.” It describes when an action occurs or how long a state continues, without necessarily implying that the action reaches completion. In formal writing, течение is written as a noun phrase, with final -е.

За can mean “in” a length of time when an action is completed within that period: сделать за час means “do it in an hour.” It can also mean “over the course of” with a completed total, as in за год многое изменилось. Use в течение to frame the time span, and за to emphasize the time needed to achieve a result.

Examples in natural speech

В течение дня я отвечал на письма.
I answered emails during the day.
В течение месяца погода менялась.
The weather changed throughout the month.
Я прочитал книгу за два дня.
I read the book in two days.
Она приготовила ужин за полчаса.
She prepared dinner in half an hour.
За год компания сильно выросла.
Over the course of a year, the company grew a lot.

Common mistakes

Do not use в течение when you mean a completion time: закончить за час means “finish in an hour,” whereas работать в течение часа means “work for/during an hour.” In careful writing, do not confuse the temporal phrase в течение with the verb течь or spell it в течении when no literal noun-case context supports that form.

Memory tip

В течение opens a time window; за measures the time needed to close the task.

Frequently asked questions

What case follows в течение?

The phrase normally takes the genitive: в течение дня, в течение года.

Does за always mean completion?

Not always, but its temporal use commonly highlights a completed result or total change within a period.

Is в течение written separately?

Yes. It is a preposition-like noun phrase and is written в течение двух недель.

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