です

です is "am", "is" and "are" in polite speech. It comes last in the sentence, after a noun or an adjective, and it has the same form whoever or whatever the sentence is about.

It is said "des": the final u is barely voiced.

Japanese has no "a" or "the", and it leaves out "I", "he" or "it" when the situation makes them clear. So がくせい学生です alone is a full sentence, and who the student is depends on who you were talking about.

The negative, the past and the negative past go in the same place, and nothing else in the sentence moves. Each has a point of its own.

After adjectives

A な-adjective takes です the way a noun does, and so do でした and ではありません.

An い-adjective needs no "is": たかい高い alone means "it is expensive". です after it adds politeness and nothing else, and it never changes. The adjective itself carries the past and the negative.

• × 高いでした → 高かったです
• × 高いではありません → 高くないです

Questions

Add か after です to ask.

Usage notes

These go beyond the basic polite sentence.

じゃ in conversation

In conversation the では of ではありません shortens to じゃ. It is still polite.

Plain speech

です is the polite form. With friends and family it becomes だ after a noun or a な-adjective, or is dropped. An い-adjective takes nothing.