Word
Книга является главным источником.
Meaning
The book is the main source.
Part of speech
sentence
Pronunciation
Course
Breakdown of Книга является главным источником.
книга
book
главный
main
являться
to be (formal)
источник
source
Questions & Answers about Книга является главным источником.
Why do we use является here instead of just using a dash, like Книга — главный источник?
While you can use a dash in everyday conversational Russian, являться is a formal verb that means "to be" or "to serve as." You will encounter it very frequently in formal writing, news reports, official documents, and academic texts.
Why are the words главным источником in the Instrumental case?
The verb являться always requires the noun and any matching adjectives that follow it to be in the Instrumental case. Even though it acts like an "equals sign" between the book and the source, it grammatically forces the second half of that equation into the Instrumental.
How do we get the specific endings for главным источником?
Both words are masculine and singular. The adjective главный (main) takes the standard masculine/neuter Instrumental ending -ым, becoming главным. The noun источник (source) ends in a consonant, so it takes the standard masculine Instrumental ending -ом, becoming источником.
Since являться means "to be", can I use it to say everyday things like "I am a student"?