The copula verb
. While it does correspond to "be
" and "equal
" in English
, it is as usual a completely different concept.
Desu doesn't at all behave like other Japanese verbs. It's so irregular as to be different part of speech altogether, which it is, as far as Japanese grammar is concerned. It has its own "conjugations" and is used all over the place. It does not form stems, bases, or have endings, in any regular sense of the word.
The general pattern for a sentence involving desu is [X] wa [Y] desu, where A is the topic of discussion and B is a definition, description, location, or somesuch. Different forms of desu are as follows:
Note that dewa
is often contracted to ja
in ordinary conversation
. Furthermore, desu
(in whatever form) can often be omit
ted; however, this renders the sentence
slightly more casual
is complicated, but among friend
s and family
you can usually leave the desu
out, whereas with stranger
s, and casual acquaintance
s you had better leave it in. It's probably better to err on the side of politeness
rather than rudeness
, anyways, in any language
Kore wa totemo oishii desu yo.
This is very tasty!
(literally: As for this, (it) is very tasty.)
Sore wa nan desu ka.
What is that?
Watashi wa ichiban muzukashii kurasu wa Nihon-go deshita.
My hardest class was Japanese.
(literally: As for me, as for number one hard class, (it) was Japanese.)
Kuruma ga hitsuyoo ja arimasen.
I don't need a car.
(literally: Car, needed, is not.)
Imooto wa aisu kuriimu ga suki ja arimasen deshita.
As for my younger sister, she didn't like ice cream.
You get the idea. You may have noticed that the verb "to be" does not appear in some of the English translations. This is because definitions and descriptions are expressed very differently in Japanese than in English, as you can see from the semi-literal translations included with some of the examples.
Desu also has some informal forms. These are da and datta, for present and past respectively. These are quite casual and should only be used among friends or certain family members, or (more likely for foreigners just visiting) not at all, except in a few fixed expressions that require them. Likewise, dewa arimasen and dewa arimasen deshita take the informal forms ja nai and ja nakatta, respectively. Da and datta are slightly more common/acceptable among groups of men, but as usual this gender difference is overrated.
Deshoo should probably be considered a form of desu, but it's a bit different and more limited, as it means "probably is".
In many cases where English uses "to be", the Japanese use one of aru, iru, or (rarely) oru, which actually correspond to "to exist" in English. This is especially true of phrases involving location, posession, or (naturally) existence, rather than definition or equality.
Desu is always written in hiragana.