です

The copula です (desu) is thought to be a contracted version of であります (de arimasu), from で (de) +‎ あります (arimasu); however, there are other possibilities, namely でございます (de gozaimasu), from で (de) +‎ ございます (gozaimasu); でする (de suru), from で (de) +‎ する (suru); でおわす (de owasu), from で (de) +‎ おわす (owasu); and でそうろう (de sōrō), from で (de) +‎ そうろう (sōrō).

• (Tokyo) です (Atamadaka – )
• IPA^(key):

です • (desu) 

1. Polite form of だ (da), after uninflecting parts of speech: to be

   これは私(わたし)のパソコンです。

   Kore wa watashi no pasokon desu.

   This is my PC.

   昨日(きのう)はいい天気(てんき)でした。

   Kinō wa ii tenki deshita.

   It was good weather yesterday.

   このパスポートはあなたのですか。

   Kono pasupōto wa anata no desu ka.

   Is this passport yours?

2. After the plain past or nonpast form of -i adjectives (or nonstandardly verbs), to form the polite ending.

   とても美(うつく)しいです。

   Totemo utsukushii desu.

   It is very beautiful.

   とてもおいしかったです。

   Totemo oishikatta desu.

   It was very delicious.

   私(わたし)も行(い)きたいです。

   Watashi mo ikitai desu.

   I want to go too.

The perfective form is でした (deshita), volitional でしょう (deshō), conjunctive でして (deshite). Other forms are not used.

Plain form of verb + です (desu) / でした (deshita) is nonstandard. The standard form is verb ren'yōkei + ます (-masu) / ました (-mashita). However, both plain form of verb + でしょう (deshō) and verb ren'yōkei + ましょう (-mashō) are valid in Standard Japanese – the former mainly expresses conjecture and the latter mainly expresses volition.

For the past tense of an -i adjective, the adjective + でした (deshita) is nonstandard and generally considered a common grammatical mistake made by non-native speakers. The standard form is instead to use the past form of the -i adjective + です (desu). For the forms ないです (nai desu) and なかったです (nakatta desu), there are synonyms ありません (arimasen) and ありませんでした (arimasen deshita).

This word is phonologically an enclitic, similar to particles. It is classified as 助動詞 (jodōshi, “auxiliary verb”) in traditional Japanese grammar.

• どす (dosu) (traditional for Kyoto)
• だす (dasu) (traditional for Osaka)

• (informal) っす (ssu)
• (affectational) ですぅ (desū)
• です体(たい) (desu tai)
• ですます体(たい) (desu-masu tai)
• ですます調(ちょう) (desu-masu chō)

• ます (masu)
• (Etymology 2, verb) だ (da)
• で候(そう) (desō)