Original Post by: olimo: https://forum.duolingo.com/comment/11536858 | Archived original page: https://archive.ph/OVWV1
olimo: I've seen so many people confused with "это" and "этот/эта/эти" that I decided to write an explanation of these. I have not seen any special post for this so far.
ЭТО - the demonstrative pronoun
It means "this/these" as in "This is a pen" or "These are ducks". Note that we don't use any equivalent of "is" in Russian, so you can even think of the pronoun-like "это" as of "this is/these are" (even if it is not exactly correct).
Examples:
- Это собака. This is a dog.
- Это мальчик. This is a boy.
- Это кошки. These are cats.
- Это моя машина. This is my car.
- Это правильный ответ. This is the correct answer.
"Это" is also used in definitions:
- Собака - это животное. A dog is an animal.
- Курица - это не рыба. Chicken is not fish.
You can omit "это" in such cases, but keep the dash.
ЭТОТ / ЭТА / ЭТО / ЭТИ - the demonstrative adjectives
They mean "this" or "these" as in "this pen" or "these ducks". These words are always used with a noun and must agree with its gender:
ЭТОТ is for masculine nouns:
этот стул = this chair
этот мальчик = this boy
этот рис = this rice
ЭТА is for feminine nouns:
эта девочка = this girl
эта тетрадь = this notebook
эта лошадь = this horse
ЭТО is for neuter nouns:
это яблоко = this apple
это море = this sea
это задание = this task
ЭТИ is for plural nouns of any gender:
эти мальчики = these boys
эти девочки = these girls
эти яблоки = these apples
What Is Confusing
You may have noted that "это" can be both a demonstrative pronoun and a demonstrative adjective of the neuter gender. So, "это яблоко" may mean both "this apple" and "this is an apple", and without context you can only tell them apart by the first capital letter and a fullstop in case it is a sentence.
это яблоко = this apple // a phrase
Это яблоко. = This is an apple. // a sentence
A Rule of Thumb
If you can replace "this/that/these/those" with "it" or "they" → use the undeclined "это" (demonstrative pronoun)
If you can't → use the declinable "этот/эта/это/эти" (demonstrative adjective)
Examples:
This is a table → It is a table? Looks fine! → Это стол.
This table is mine → It table is mine? No way! → Этот стол мой.
These are books → They are books? Looks fine! → Это книги.
Are these books yours? → Are they books yours? No way! → Эти книги ваши?
Declensions
For those who already made it to the Russian case system, here is the declension table for the demonstratives. I placed neuter next to masculine because their forms are the same in many cases.
https://www.dropbox.com/s/j9qcquawa0cahr1/eto.png
Sorry, Dropbox has broken something and I can't paste it as a picture any more.
The accusative forms written with a slash are for animate/inanimate nouns (like "этого кота / этот стол").
Hope this helps!