7.4. Copula


A copula is a special word that combines the subject of a sentence and its description. Copulas are often irregular in many languages. The English word be is a copula. It is the verb whose inflection is most irregular in English. It combines the subject and its description, such as "Apples are fruits" and "The sky is blue". However, the word is in "The book is on the desk" is not a copula but an existential verb similar to the verb exist.

The plain copula in Japanese is (da) "da". It is not a verb but a suffix added to nouns.
Here is an example of the copula:

Kana: (to)(u)(ki)(small yo)(u)(ha)    (si)(small yu)(to)(da) (period)
Romanization: kyôwa syutoda.
Structure: noun
(Tôkyô)
topic
marker
noun
(capital)
copula
(is)
Meaning:Tôkyô is capital.

Since the copula (da) "da" is not a verb but a suffix, the combination of the noun (si)(small yu)(to) "syuto" and the copula works as if it were a verb. It is important to treat them as a single predicator. You cannot make a pause between the noun and the copula, and you cannot move the noun from the position immediately before the copula. In other words, the copula (da) "da" makes a noun work like a verb.

The copula has inflection like verbs, but it is highly irregular. The past form of (da) "da" is (da)(small tu)(ta) "datta".

Here is an example of the past form of the copula:

Kana: (ki)(small yo)(u)(to)(ha)    (si)(small yu)(to)(da)(small tu)(ta) (period)
Romanization: Kyôtowa syutodatta.
Structure: noun
(Kyôto)
topic
marker
noun
(capital)
copula
(was)
Meaning:Kyôto was capital.

Kyôto, a city 400 kilometers west to Tôkyô, was capital of Japan from 794 to 1192.


The polite form of (da) "da" is (de)(su) "desu". Its stem is "des" and the last "-u" is the suffix for the nonpast form. Its inflection is almost the same as the polite suffix (ma)(su) "masu", and its past form is (de)(si)(ta) "deshita".

Kana: (to)(u)(ki)(small yo)(u)(ha)    (si)(small yu)(to)(de)(su) (period)
Romanization: kyôwa syutodesu.
Structure: noun
(Tôkyô)
topic
marker
noun
(capital)
copula
(is + polite)


Kana: (ki)(small yo)(u)(to)(ha)    (si)(small yu)(to)(de)(si)(ta) (period)
Romanization: Kyôtowa syutodesita.
Structure: noun
(Kyôto)
topic
marker
noun
(capital)
copula
(was + polite)


The original form of the copula helps us to understand its irregular inflection. The modern copula (da) "da" comes from the old style copula (de) (a)(ru) "de aru", which is a combination of the word (de) "de" and the existential verb (a)(ru) "aru". The word (de) "de" came from the ancient postposition (ni)(te) "nite", but now it is considered a form of the copula which uses the existential verb as an auxiliary verb just to give tense to a sentence.

Since (a)(ru) "aru" is a regular Group I verb, its inflection is easy to understand like these:

Kana: (to)(u)(ki)(small yo)(u)(ha)    (si)(small yu)(to)(de)    (a)(ru) (period)
Romanization: kyôwa syutode aru.
Structure: noun
(Tôkyô)
topic
marker
noun
(capital)
copula
(be)
auxiliary
verb
(nonpast)


Kana: (ki)(small yo)(u)(to)(ha)    (si)(small yu)(to)(de)    (a)(small tu)(ta) (period)
Romanization: Kyôtowa syutode atta.
Structure: noun
(Kyôto)
topic
marker
noun
(capital)
copula
(be)
auxiliary verb
(past)

The old style copula (de) (a)(ru) "de aru" is scarcely used in spoken Japanese, but it is still often used in written Japanese. Its polite forms are not commonly used even in written Japanese.

To summarize, the modern copula and its polite form are derived as follows:

FormThe original copulaThe contracted copula
Nonpast
(de)  (a)(ru)
dearu
(da)
da
Past
(de)  (a)(small tu)(ta)
deatta
(da)(small tu)(ta)
datta
Polite nonpast
(de)  (a)(ri)(ma)(su)
dearimasu
(de)(su)
desu
Polite past
(de)  (a)(ri)(ma)(si)(ta)
dearimasita
(de)(si)(ta)
desita



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