Noun + 이다 grammar - Noun + ida grammar

이다 is similar to the English verb ‘to be’ (i.e. ‘is’, ‘are’, ‘am’, etc.). It is an equational/identification expression and is only attached to nouns.

e.g:
English: A is B
Korean: A B[to be] -> AB이에요/예요

The different conjugations for 이다 are:

• Formal descriptive: 입니다
• Formal interrogative: 입니까?
• Informal descriptive/interrogative: 이에요/예요(?)
• Casual descriptive/interrogative: 이야/야(?)

이에요/예요

Deciding when to use 이에요 or 예요 (or 이야/야) is dependent on whether the last letter of the word/noun is a vowel or consonant, just to make pronunciation easier.

• 이에요 (or 이야)  is used when the last letter ends in a final consonant
• 예요 (or 야) is used when the last letter is a vowel

In summary:

Final consonant + 이에요 
Vowel + 예요

Sample sentences (Taken from TTMIK Level 1 Lesson 5)

물이에요. = (It’s) water.
가방이에요. = (It’s) a bag.
사무실이에요. = (It’s) an office.
학교예요. = (It’s) a school.
Robert이에요. = (I’m) Robert

When using the informal and casual conjugations, the sentences can be made into a question simply by raising the tone at the end of the sentence:

물이에요? = (It’s) water?
뭐예요? = What’s is it?