～ないです

～ないです makes a polite negative by taking the plain negative (the ない-form) of a verb or adjective and simply adding です. It means the same thing as the textbook negative ～ません, but sounds softer and more conversational.

In English both come out as a plain “don’t / isn’t” — the difference is only in tone: 行きません is a bit more formal, 行かないです is everyday polite speech.

1. With verbs

Take the verb’s ない-form and add です.

2. With い-adjectives

い-adjectives form their negative with ～くない, and adding です makes it polite. This is the standard polite negative for adjectives.

How to form it

Verb ない-form + です / い-adjective ～くない + です

• 行く（いく）= to go → 行かないです（いかないです）= don’t go (polite)
• 食べる（たべる）= to eat → 食べないです（たべないです）= don’t eat (polite)
• 高い（たかい）= expensive → 高くないです（たかくないです）= is not expensive

Key idea

です after a plain negative is a politeness sticker: the meaning stays exactly the same as the plain ない-form, but the sentence becomes polite. When in doubt in conversation, ～ないです is a natural, friendly alternative to ～ません.