Quick answer
Э́то = “this is”, and it never changes: Э́то кни́га. Э́тот = “this”, pointing at a noun, and it agrees with it: э́тот стол, э́та кни́га, э́то окно́.
The forms of э́тот
| Masculine | Feminine | Neuter | Plural | |
|---|---|---|---|---|
| this | э́тот | э́та | э́то | э́ти |
| that | тот | та | то | те |
Note the trap: the neuter э́то is spelled exactly like the unchanging э́то that means “this is”.
Side by side
Э́то кни́га.This is a book. — introducing it
Э́та кни́га интере́сная.This book is interesting. — pointing at it
Э́то мой брат.This is my brother.
Э́тот челове́к — мой брат.This man is my brother.
Ско́лько сто́ит э́та ку́ртка?How much is this jacket?
Typical mistakes
Э́тот кни́га интере́сная.
Э́та кни́га интере́сная.
э́тот agrees with the noun: кни́га is feminine.
Э́та мой брат.
Э́то мой брат.
For “this is”, the frozen э́то is always right.
Check yourself
___ кни́га интере́сная. — This book is interesting.
Pointing at a feminine noun: э́та.