"Suddenly I forgot what I wanted to say."
Translation:Я вдруг забыл, что хотел сказать.
Why don't we need то here? I feel like "Я вдруг забыл, что хотел сказать" should mean "Suddenly I forgot THAT I wanted to say", which seems incomplete.
I somehow have it in my head that "то, что"="that which"="what", whereas [глагол]+что=[verb]+that.
So, for example: Я знаю, что ты сказал что-то. = I know that you said something. and Я знаю то, что ты сказал. = I know what you said./I know that which you said.
So is "Я вдруг забыл ТО, что хотел сказать" (to mean "Suddenly I forgot what I wanted to say") wrong?
If they're both right, can I just be lazy and forget то in such situations?
In standard Russian, «Я вдруг забыл, что ты хотел сказать» can mean two things:
(1) If «что́» is stressed, then «Я вдру́г забы́л, что́ хоте́л сказа́ть» means 'I suddenly forgot what I wanted to say.' (Note that we normally don't put stress under one-syllable words. However, here «что» is stressed.)
(2) If «что» is not stressed, then «Я вдру́г забы́л, что хоте́л сказа́ть» means 'I suddenly forgot that I wanted to say [something obvious from the context]'. This sentence is incomplete: you don't normally use «сказа́ть» without an object. It works only if the previous sentences supplied some context that makes the object obvious.
You can add «то» in the first meaning, and it's also correct standard Russian:
(3) You can use «Я вдру́г забы́л то́, что́ хоте́л сказа́ть» 'I suddenly forgot that [thing], which I wanted to say' in this meaning, too. In standard Russian, this variant places more emphasis on «то́».
In colloquial speech, especially among younger people, «то» is becoming required, and a new conjunction «то́ что» is appearing, sometimes replacing «что» in its functions. This transformation is not yet finished: some people might have this new conjunction, but many others don't. This change has not yet happened in standard Russian.
Upd.: my previous text said that «то́ что» is only used in place of (1). This is in fact not correct, it can be used in place of (2) sometimes, too.
Maybe we’re dropping the pronouns ourselves in casual speech. I don’t personally think I do it often, but such things often go unnoticed.
For example, according to , Russian speakers often mix Genitive and Prepositional (and sometimes Dative) cases. This book has lots of examples of news presenters using things like «А сейчас мы возвращаемся к главной темы» in the news broadcast. Try reading this to your friends and you’ll see that most people would say: «This book is wrong! We don’t speak like that!». Because such things do go unnoticed.
So pronoun-dropping may be something most people do in colloquial speech (which I personally doubt), but we wouldn’t admit it because it’s not something we’ve learnt at school, it’s not something we see in books. It’s an insiduous colloqualism that we don’t notice. Sometimes foreigners notice such things better than we do, because they didn’t go to our school and didn’t learn the outdated views on how we're supposedly speaking.
However, even if this is a way we speak (which needs to proven), it's probably not something you want to learn, because native speakers are able to switch to a standard Russian when such a need happens. And we often do. But if you learn colloquial Russian and not standard Russian, you won’t be able to make such a switch.
Standard Russian is better for learners because you can use it on all occasions. If you use colloquial Russian on formal occations, this will sound very wrong. If you use standard Russian on colloquial occasions, you will sound like an educated person that makes an effort to speak correctly.
So, this course attempts to teach standard Russian. Yes, sometimes it’s not how we really speak, but it’s how we’re supposed to speak.
 Современный русский язык: Активные процессы на рубеже XX-XXI веков. — М.: Языки славянских культур, 2008. — 712 с. — (Studia philologica), available here: http://sci.house/russkiy-yazyik/vzaimovliyanie-padejey-69883.html
Russian verbs used in the past tense only agree with the number/gender of the subject. With "I" or "you" it depends on the sex of the person you are referring to. You cannot know it without any context given: both Я забыл and Я забыла would simply be "I forgot" in English.
- the past forms of the Russian verbs are etymologically former participles (it's like saying "I seen that" in English—Russian lost the auxiliary verb), so they behave very similar to short adjectives.