I am trying to understand the difference between -нибудь and -то and I've found the following explanation:

1) when a sentence is interrogative, imperative or in the future, you should use -нибудь
(Возьми что-нибудь почитать, Я куплю какой-нибудь журнал, Вы поедете куда-нибудь летом?)

2) if the sentence is in the present or in the past tense, you should use -то
(Нам надо прочитать какой-то рассказ, но я не помню какой - я что-то читал об этом)

Does it make any sense? Thanks 🙏

Question

I am trying to understand the difference between -нибудь and -то and I've found the following explanation:

1) when a sentence is interrogative, imperative or in the future, you should use  -нибудь
(Возьми что-нибудь почитать, Я куплю какой-нибудь журнал, Вы поедете куда-нибудь летом?)

2) if the sentence is in the present or in the past tense, you should use -то
(Нам надо прочитать какой-то рассказ, но я не помню какой - я что-то читал об этом)

Does it make any sense? Thanks 🙏

tagiltsevans · Answer

-Нибудь  if not matter what/who exactly
Кто-нибудь, помогите!
I just need help. Any person can help me, I would be glad

-То if you don't know who/what exactly
Там кто-то есть!
Я что-то слышу!
Я на что-то наступил!
I know that something /somebody is there, but I don’t know wh, but it does matter. If it my friend, I will glad, if it's some wild animal, I'm in trouble

Palaver · Answer

That may sound like a neat guideline but it's not very precise in actual fact. The rule regarding tenses doesn't directly apply except to temporal pronouns, too.

Here's some explanation for ya:

Strictly speaking, -нибудь indicates an unspecific entity whose very existence is undetermined (it may or may not exist), while -то indicates an unspecific entity that is at least assumed to exist. This is the basic observation forming the difference between the two pronoun groups.
(For further reference, кое- indicates a specific entity the speaker knows but doesn't name outright, e.g. Я сегодня кое-кого встретил. = I met someone today. [I know who I met, obviously, so it's a specific person - I just don't name them in the sentence.); -либо indicates an unspecific entity of undetermined existence like -нибудь, traditionally used in questions and if-clauses, however in the modern language it can freely be replaced by -нибудь, hence using -либо gives the sentence a formal or lofty feeling.)

Hence, -нибудь is preferred in questions and statements that do not assume the existence of the object, such as if-clauses, while -то is preferred in statements otherwise. However, it is not uncommon to use -то in questions with the implication that the object you're talking about probably exists, and it is fairly common to use -то in statements without a specific implication that the object referred to by the X-нибудь pronoun necessarily exists. E.g. Ты что-нибудь потерял? / Ты что-то потерял? ~ Did you lose anything/something? (The latter question implies the speaker feels the answer is probably yes, I did lose something. Some similarity to 'anything' vs 'something' in English, although not a one-to-one comparison.)

You still must use -то when the entity that the pronoun refers to definitely exists or is assumed to exist, e.g. Я где-то потерял ключ. = I lost my key somewhere. (I know I lost it, hence that "somewhere" definitely exists.) Там кто-то есть. = There is someone there. (I think that 'someone' exists, hence I use -то.) But compare: Проверь, есть ли там кто-нибудь/кто-то. = Check if someone is there. (Strictly speaking, you do not assert that "someone" exists, hence -нибудь would be used, however it is perfectly common in the modern language to use -то as well in such a sentence, without a particular implication that such a "someone" must exist.)

You also must use -нибудь when the entity cannot be presumed to exist, e.g. Кто-нибудь, помогите мне! = Anyone help me! (I am calling out for anyone that may help, without presuming such a person exists (i.e. that someone will come and help). In fact, I don't think you can address кто-то in an imperative sentence like that, unless you're addressing a specific person you don't know (e.g. someone hiding in the bushes - you know someone is there without knowing who that person is).) However, compare again: Мне может кто-нибудь/кто-то помочь? = Can (may, could) anyone help me? (Again, strictly speaking you do not assert that person exists so -нибудь would be used, but in the modern language it is perfectly common to use -то in such a sentence as well; in this case, with a mild implication that such a person has to exist, i.e. that someone ought to come and help me indeed.)

The observation concerning time is only strictly true for the temporal pronouns/adverbs когда-то / когда-нибудь (at some point, 'somewhen'). Когда-то refers to an unspecified point in time in the past, while когда-нибудь refers to an unspecified point in time in the future. This is because the former is by definition asserted to exist, having been in the past; while the latter is again by definition not presumed to necessarily exist, being in the future that is yet to happen.

olga84 · Answer

Моё мнение: 
"кто-то" - это фигура конкретная (хотя мне неизвестная), а "кто-нибудь" - это уже не просто неизвестная лично мне фигура, а уж и вовсе никак не определенная.

Например: 
Кто-то выкинул собаку на улицу, но кто-нибудь другой может взять её себе.
Кто-нибудь выкинет собаку на улицу, а она прибежит к нам, и мы возьмем её себе.

Marina_SJ · Answer

Вот здесь нашла хорошее объяснение:

Случаи, в которых надо использовать: 
1.
–ТО: Когда ты не знаешь или не помнишь кто, что, где это было. 
Пример: Я где-то тебя уже видела. (Но точно не знаю где. Или не помню где.)
2.
–НИБУДЬ: Когда не важно кто, что или где. 
Пример: Дай мне что-нибудь поесть. (Мне не важно что.)

Marina_SJ · Answer

@olga84 логично, но я вот думаю, а как насчёт: "Если кто-то выкинет собаку на улицу, будет иметь дело с зоозащитниками"? 🤔 Фигура гипотетическая.

Alex_Nikolaev · Answer

As for me , it doesn't make any sense :) I may say "надо прочитать какой-нибудь рассказ"

Alex_Nikolaev · Answer

@semsaudade Возьми что-нибудь почитать =Возьми что-то почитать / Вы поедете куда-нибудь летом = Вы поедете куда-то летом But you can't say Я куплю какой-то журнал. Actually you can... in some cases. but... nevermind :)