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Verb To Be 이다 in Korean

Unlike English, Korean makes no distinction for the choice of verb to be (am, are, is) between first-person, second-person and third-person subjects. Only a single verb to be 이다 is used.

We only attach 이다 (or its modified forms) to nouns and noun phrases. Korean adjectives are verb-like and do not require 이다 for sentence construction.

Summary for Korean Verb To Be 이다 (Present, Past, Present Negative)

Speech Level Plain Form Formal Polite Informal Polite Formal Casual Informal Casual
is, am, are 이다 입니다 이에요/예요 인다 이야/야
was, were 이었다 이었습니다 이었어요 이었다 이었어
is not, am not, are not 아니다 아닙니다 아니에요 아닌다 아니야

Recall that the subject of a sentence can be omitted (if it is understood by the context), and verb is always at the end of a Korean sentence.


The Korean sentences above with different speech levels convey the same meanings. Notice that (book) is a noun in the sentences.

The choice of 이에요/예요 and 이야/야 is based on Consonant-Vowel Sequences in Spoken Korean.

  • If the noun ends with a vowel, use 예요 or 야.
  • If the noun ends with a consonant, use 이에요 or 이야.

Verb To Be だ and です in Japanese

To study this grammar point, please make sure you understand the following:

Unlike English, Japanese makes no distinction for the choice of verb to be (am, are, is) between first-person, second-person and third-person subjects.

Nonetheless, Japanese grammar distinguishes between plain (casual) form and polite form by either the choice of words, or the modified form of the words.

The plain form for is, am, are in Japanese is . The polite form, which is more common in introductory textbooks, is です.

However, the plain form だ and its modified forms are way more important for Japanese grammar, and students should understand their usages.

The plain form verb to be だ and its modified forms are very important in understanding Japanese grammar.

Summary for Japanese Verb To Be (Present, Past, Present Negative)

is, am, are was, were is not, am not, are not
Plain Form だった じゃない
Polite Form です でした じゃないです or ではありません

Is, Am, Are (Present Tense)

  • plain form: だ
  • polite form: です

Recall that the subject of a sentence can be omitted (if it is understood by the context), and verb is always at the end of a Japanese sentence.

学生だ。
I am a student.
(casual form)
学生です。
I am a student.
(polite form)

Notice that 学生 (student) is a noun in the sentence. For adjective in such a sentence, such as I am fine, the rules are slightly different. You can learn it from sections for い-adjectives and な-adjectives.

You can also use a noun without any verb to be. It is still a good sentence.

学生。
I am a student.
(casual form)

Was, Were (Past Tense)

  • plain form: だった
  • polite form: でした
学生だった。
I was a student.
(casual form)
学生でした。
I was a student.
(polite form)

Is Not, Am Not, Are Not (Present Negative)

  • plain form: じゃない
  • polite form: じゃないです or ではありません
学生じゃない。
I am not a student.
(casual form)
学生ではありません。
I am not a student.
(polite form)

Notice that じゃないです is the more common spoken form, and ではありません /dewa-arimasen/ is more formal form for the written format.

Was Not, Were Not (Past Negative)

It is the same rules to derive the past-negative form for い-adjectives (because the suffix ない can be considered as an い-adjective).