です

From WagaWiki

です is a copula, or a word (verb) that connects two words. The best equivalent in English would be the verb "to be". However, です can often be used as merely a politeness marker which has no English equivalent. It is not conjugated like the other verbs.

Conjugation

です goes at the end of a sentence to mean "to be (is, are, etc.)". It is conjugated in the present and past as so:

Present Affirmative: です
Present Negative:　ではありません
Past Affirmative: でした
Past Negative: ではありませんでした

The plain form of です, だ, also has somewhat irregular conjugations:

Present Affirmative: だ
Present Negative:　ではない (じゃない in spoken language)
Past Affirmative: だった
Past Negative: ではなかった (じゃなかった in spoken language)

Example Sentences