I've noticed that constructions with "надо" tend to use a perfective form of a verb. Is there some sort of loose grammar rule dictating this? Or does it just depend on context? For example, can I use either one of the following:

Мне надо помыть четырех кошек.
I need to wash four cats.

Мне надо мыть четырех кошек.
I need to wash four cats.

My experience with Russian thus far is that its meanings are often quite precise, so I can't imagine that the two sentences above mean exactly the same thing, but I've seen "надо" paired with both (and the English translations for each), even though I have not yet seen any sort of pattern that distinguishes "надо помыть" from "надо мыть".

After a visit to Wiktionary, I now know that the construct "не надо" is

used in combination with imperfective infinitive verbs.

but that doesn't fully explain all the instances I've seen of "надо" paired with imperfective infinitives. Here's an example:

Безусловно, перед едой надо мыть руки.
Sure. Everyone washes their hands.

Example from Reverso's search results for sentences with "надо мыть" in them.

As always I appreciate any insight you can provide and want to stress that I'd love to see answers that also go beyond the two examples given above and discuss any details that might pertain to "надо" + verb constructions in a more general sense but are still relevant to this question. To start with, what part of speech do Russian linguists/grammarians assign to "надо"?

Thank you in advance.

BTW, I've been to the following discussion threads:

Difference between нужно и надо

Usage patterns of “надо” vs. “нужно”

If they answer the questions I've asked in this post, I didn't see it.


7 Answers 7


Надо + imperfective emphasizes the process (I have to work on this) while надо + perfective has an emphasis on the result and what follows (I have to get it done). The reason for that can differ, for example:

Certainty or lack thereof about job size:

Мне надо помыть кошек, и тогда я смогу пойти обедать.
I have to make sure [all the] cats are clean then I’ll be able to have dinner.

Мне надо мыть кошек, пока кошки не кончатся.
I have to occupy myself with washing [some] cats until I run out of cats.

Job being one-off or being part of one’s life:

Мне надо помыть кошек, чтобы не пачкали мебель.
I have to make sure cats are clean [once and for all] so they don’t stain the furniture.

Мне надо мыть кошек ежедневно.
I have to occupy myself with washing [those mud-loving] cats every day.

Thus perfective forms are more common after надо. After не надо it makes no sense to use perfective: “I don’t need to do X” is OK, while emphasizing “I don’t need to achieve X” would be strange.

  • 1
    I was really very close to giving Abakan the green checkmark, even though it simply reinforced what I'd already read about the difference between the perfective/imperfective aspects of a verb. Your answer, as short as it was, actually addressed the part of my question that wanted to know how the perfective and imperfective interact with "надо" constructions. And for that, the green checkmark goes to you. I don't always favor the shorter answers and often reward those who have clearly done a lot of research, but in this case, I think the information you've provided answers the question best. TY
    – Lisa Beck
    Nov 23, 2017 at 21:06

You use perfective verbs when you are talking about a task that you have to complete once:

Мне надо помыть четырёх кошек (и потом я могу отдыхать).

And you use imperfective verbs when you are talking about tasks that you do on a regular basis:

Мне надо мыть четырёх кошек (каждую неделю).

Or, for your example:

Перед едой (каждый раз) надо мыть руки.

  • 4
    You should correct your examples "четырех кошек"
    – V.V.
    Oct 2, 2017 at 17:13
  • 5
    @V.V. - as long as he translates it as "cats" and not "grappling hooks" :)
    – Alexander
    Oct 3, 2017 at 0:35
  • 2
    Do those also need washing?
    – V.V.
    Oct 3, 2017 at 6:57
  • 3
    Being a Russian native speaker I found this answer educative and useful, learned something new today :) I mean if I was asked the same question I wouldn't be able to answer it better Oct 3, 2017 at 14:07
  • 1
    @LisaBeck I can't imagine a situation when you don't know that. But if you mean both, the more immediate comes first and then you would add the second infinitive. В субботу мне надо помыть кошек, а потом я буду их мыть каждый вторник.
    – V.V.
    Nov 25, 2017 at 7:33

I think, perfective means once, imperfective means continued or repeated action.

Мне надо помыть четыре кошки.
I need to wash four cats, and once it's done I'm all set.

Мне надо мыть четырёх кошек.
I need to wash four cats once in a while.

When in doubt, use perfective (you can't make sure all four cats will be available next time)

"не надо" isn't paired with perfective verbs usually since it doesn't make sense to start the process if you should not have it completed.

There are counterexamples in question form, though.

Мне помыть апельсин? Не надо!
Should I wash this orange? Please don't!
  • 1
    Is there any reason why you use четыре кошки in the first sentence but четырёх кошек in the second? Oct 2, 2017 at 14:36
  • 1
    @PeterOlson IMO it sounds more natural since кошка is animate. But you can use either one. See russian.stackexchange.com/questions/9071/…
    – alamar
    Oct 2, 2017 at 14:42
  • 1
    Does it only sound more natural with the imperfective verb? It confused me a little that the sentence with the perfective verb uses one form and the sentence with the imperfective verb uses another form. Is the form chosen related to the aspect of the verb? Oct 2, 2017 at 14:46
  • 1
    @PeterOlson for some reason, with perfective verb четыре кошки were tolerable to my ear but with imperfective the bell rang. I can imagine that there's more activity in four cats being washed repeatedly and so there's more nagging to acknowledge that :) Of course, if it's terracotta cats you can always wash them as четыре кошки
    – alamar
    Oct 2, 2017 at 15:00
  • 6
    This is accusative tense that uses different endings for animate and inanimate nouns. So, you should say (по)мыть четырех кошек, но (по)мыть четыре двери.
    – ulu
    Oct 2, 2017 at 15:22

It's not "помыть четыре кошки", it's "помыть четырех кошек", because 'cat' is animate. People and animals are animate, so you need to account for that in the accusative case:

А у одушевленных существительных женского рода окончания будут: нулевое или –ей, например: женщины- женщин, студентки - студенток, матери – матерей

При этом если два согласных стоят рядом, в винительном падеже между ними для благозвучия появляются гласные «о» или «е», как: Белки- белок, девушки – девушек.

Funny thing is that this example is about girls (девушек), but the concept is exactly the same: feminine + animate - кошек

You might wish to use the examples of ... and complete exercises here:


"Надо" can be used with both a perfective and imperfective infinitive:

Я думаю, мне надо накормить тех четырех кошек, их хозяйка до завтра не вернется. I think I should feed those four cats. Their owner will not be back till tomorrow.

This is the perfective form, we are talking about one occurrence of a feeding.


Мне теперь надо кормить этих четырех кошек, а у меня своих дел полно! Now I have to feed these four cats, and I have other things to do!

It's exactly the same meaning as following:

Теперь мне придется кормить этих четырех кошек.

Note that in neither case of imperfective infinitive usage is it clear whether we are talking about feeding for an indefinite period of time, or just one meal. It can only be made clear from the context, not from the fact that it's an imperfective infinitive.

Не надо брать себе чужих кошек, и все будет в порядке!

Don't take responsibility for cats you don't own and you will be fine.

Мне обязательно надо покормить этих четырех кошек до 15:00, иначе они разнесут дом по щепочке!

Have to feed the four cats before 3PM (TODAY), otherwise they will turn the house into chips!

In this case it's definitely about just one feeding, the verb is in the perfective form, and today is not necessary in the Russian variant.

С кошками надо быть добрее!

Got to be nice to cats!


Мне надо помыть четыре кошки means I need to start and complete the washing. In opposite, Мне надо мыть четыре кошки may mean I have to start but I do not have to completely wash them. I might start for example to wash but do it partly. That's why "не надо" is usually used with imperfective infinitives: one should not start the action at all.


Sometimes you can use "надо" with the imperfect form to express the continuity of the process. Compare:

Мне надо вымыть посуду.

(sort of "future perfect", meaning we're interested in the result)

Мне надо быть в хорошей форме

(sort of future/present continuous, i.e. we're interested in the process)


"I need to get those cats washed". - perfective


"I have to wash those cats [every day]." - imperfective

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