Desu vs Da Practice: Noun Sentences in Plain and Polite Style

Change noun predicates between plain and polite forms while preserving tense and meaning. Keep this pattern separate from the endings of verbs and い-adjectives.

Change the predicate, not every sentence ending

学生です is a polite noun predicate; 学生だ is its plain counterpart. The past forms are 学生でした and 学生だった. These changes belong to the predicate, so they cannot be made by replacing an unrelated word near the beginning of the sentence.

With い-adjectives, おいしいです becomes おいしい in plain style, not おいしいだ. With verbs, 行きます becomes 行く, not 行くだ. Plain style and polite style each contain several patterns. Learning だ as a universal “casual ending” creates errors.

Use one situation consistently

Imagine telling a friend that yesterday was a holiday, then reporting the same fact to a new acquaintance. The tense stays past; the level of politeness changes. For the negative answers below, the prompt specifies the particular construction so that alternative natural negatives are not marked wrong without explanation.

Examples to read before you practise

Try six questions

Use the interactive practice below. Type only the requested expression. Kanji and kana alternatives are accepted where listed in the answer key. Completing a question records a result; opening the answer key does not.

1. 学生です → plain affirmative noun predicate

2. 雨だ → polite non-past

3. 休みです → polite past

4. 学生だ → plain past

5. おいしいです → plain affirmative

6. 学生です → polite negative using ではありません

Answer key and explanations

1. 学生だ / がくせいだ — A plain affirmative noun predicate ends in だ.

2. 雨です / あめです — A polite noun predicate takes です.

3. 休みでした / やすみでした — The polite past of です is でした.

4. 学生だった / がくせいだった — The plain past of だ is だった.

5. おいしい — Do not add だ to this い-adjective.

6. 学生ではありません / がくせいではありません — This prompt asks for the ではありません negative.

Keep learning

• Study desu da.

• Study plain polite.

• Open this six-question practice set.

• See your daily study and review schedule.

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