〜です

an auxiliary verb for a polite sentence-ending expression

1. Overview

"〜です" is one of the most common expressions in Japanese, used to add politeness to the sentence. It is often compared to the informal "だ" used in casual speech. "です" is used in neutral or formal contexts and is a key part of Japanese polite language (丁寧語).

2. Structure

Type	Example	Translation
Noun + です	彼は学生です。	He is a student.
い-adjective + です	今日は寒いです。	It is cold today.
な-adjective + です	この映画は有名です。	This movie is famous.
Verb (polite form)	私は行きます。	I will go.

Explanation:
- Used after nouns or adjectives to form a polite statement.
- The verb "です" does not conjugate much on its own but can take other forms to change tense or negate a sentence.

3. Usage Explanation

Function: "です" adds formality and politeness to a sentence, making it appropriate for neutral or formal contexts. It is frequently used in daily conversation to avoid sounding too casual or abrupt.
Usage in Speech: In informal settings, "です" can be replaced with "だ" when speaking to friends or people of lower social standing. However, in business, work, or with strangers, "です" is preferred to maintain politeness.
Conjugation:
- Present affirmative: 〜です
- Present negative: 〜ではありません / じゃありません
- Past affirmative: 〜でした
- Past negative: 〜ではありませんでした / じゃありませんでした

4. Key Points to Note

Formality:
- "です" is more polite than "だ" and should be used in polite or formal contexts.
- It's important to maintain this form in situations where social hierarchy or respect is important, such as in workplaces or when speaking to strangers.
Negative and Past Forms:
- "です" itself cannot be used directly to negate a sentence. Instead, use "ではありません" or "じゃありません" for negative sentences.
- For past tense, change "です" to "でした."

5. Example Sentences

彼女は先生です。
She is a teacher.
今日は天気がいいです。
The weather is nice today.
このレストランは美味しいです。
This restaurant is delicious.
あの映画は面白かったです。
That movie was interesting.
彼は学生ではありません。
He is not a student.

6. Summary

"〜です" is an essential part of Japanese polite speech, adding a level of formality to statements. It is used in both formal and neutral contexts, and it is critical to know its proper usage to communicate appropriately in various social situations.