One interesting and very common use of unchanging это is to refer to a situation broadly. Consider this sentence:
|Я всю ночь не спал из-за шума. Это опять были наши соседи.||I didn't sleep all night because of the noise. It was our neighbors again.|
Although «Это были наши соседи» and “It was our neighbors” resemble each other superficially, they are grammatically quite different. In the English sentence “it” is the subject, singular “was” agrees with “it”, and “neighbors” is a predicate noun in the plural. In the Russian sentence соседи is the subject and induces verbal agreement. Notice that это does not agree in gender with anything in the sentence that precedes it. It's not referring to the night. It's not referring to the noise or the neighbors. It refers to the whole, abstract situation. Here are a couple other examples.
|Сегодня в два часа ночи в дверь постучали. Это была моя сестра.||At two o'clock in the morning there was a knock at the door. It was my sister.|
|Зимой 1970-ого года я жил в Норильске. Это был ад. Собачий холод, шесть недель совсем не было солнца, и даже местный самогон не мог облегчить нашу скуку.||In the winter of 1970 I lived in Norilsk. It was hell. It was miserably cold. For six weeks there was no sun at all, and not even the local homebrew could relieve our boredom.|
This use of unchanging это is not limited to “be” sentences. For instance, in Crime and Punishment Raskolnikov confesses with this phrase:
|Это я убил старуху.¹||It was I who killed the old woman.|
This use is a bit different than the one we discussed earlier because instead of referring to a whole abstract situation, это serves to direct the listener's focus on the identity of one particular person in the situation:
|Когда мы были детьми, это папа покупал продукты, а не мама.||When we were kids, it was Dad who did the shopping, not Mom.|
|Это брат просит картинки показать, а не я.||It's my brother who is asking you to show us the pictures, not me.|
¹ The precise quote is «Это я убил тогда старуху-чиновницу и сестру ее Лизавету топором и ограбил.» “It was I who killed the old woman and her sister Elizabeth with an axe and robbed them.”
The number of native Russian words that start with э is very small. In that sense it is one of the most uncommon letters in Russian… except for the fact that it is the first letter of это, and это is one of the most common words in Russian. Weird, eh? Something similar is true in English. The number of English words that start with the sound [ð] is very small, but it is the first sound in the English word the, which is among the most common English words. That's really got nothing to do with today's topic, but I've always wanted to say it.
One of the little difficulties for us foreigners studying Russian is to figure out when we need to change это to agree with a noun, and when not. It's confusing because really there are two different это words in Russian. The first we will call “unchanging это,” which has only one form, and the other we will call “adjectival это,” which has endings that change for case, number, and gender. The neuter singular form of adjectival это is spelled the same as unchanging это, and that's where the confusion lies.
Unchanging это is first of all used in the phrase «Что это?», which can be translated quite a few ways, depending on the number of things the questioner is asking about:
|Что это?||What is this?
What is that?
What are these?
What are those?
Likewise in the response to those questions, это can be translated quite a few ways:
|Это — журнал.||This is a magazine.
That is a magazine.
|Это — книга.||This is a book.
That is a book.
|Это — письмо.||This is a letter.
That is a letter.
|Это — журналы.||These are magazines.
Those are magazines.
Thus unchanging это can be translated as this, that, these, or those, depending on context. Now notice that in the English translations of those sentences above, whenever we are dealing with unchanging это, the this/that/these/those in English is separated from the noun it refers to by a form of the verb “to be.” That's going to be our rule of thumb for identifying unchanging это:
Rule of thumb: When “this” (or that/these/those) is separated from its noun by a form of “to be,” use unchanging это in Russian.
Unchanging это also appears in какой and чей questions. Here there is a quirk in Russian word order. For instance, an American might expect the translation of “What kind of car is that?” to be «Какая машина это?», where какая agrees with машина in gender and number, and where we use unchanging это because “that” is separated from машина by “is.” That's true as far as it goes. But for some reason the Russians always like to move the это to a position immediately after the question word:
As to adjectival это, it has the following forms:
We use adjectival это to directly modify a noun. When translating adjectival это, there is no form of the verb “to be” between this-these and its noun:
|Эта книга очень интересная.||This book is very interesting.|
|Ты когда-нибудь читала эту книгу?||Have you ever read this book?|
|Мы уже давно живём в этом доме.||We have been living in this building for quite some time.|
|Под этой лестницей живёт кошка-мамочка и четверо котят.||A mama cat and four kittens live under this staircase.|
Adjectival это is also used in phrases equivalent to colloquial English “this one” and “these ones”:
|У меня два батончика. Этот для меня, а тот для тебя.||I have two candy bars. This one is for me, and that one is for you.|
|— Что ты думаешь об этих машинах?
— Ну, эта нравится, а та — нет.
|“What do you think about these cars?”
“Well, I like this one, but not that one.”
Unchanging это has one more quirk. We'll address it in a day or two.