As I understand 都市 [toshi] means [city].
And therefore it could be any city, which is not town.
In Russia town means over 12K population.
100-250K pouplation = big town.
250-500K pupulation = small city.
500K-1M population = city.
> 1M population = large city = megapolis.
There is Japanese word 大都市 [daitoshi] which means large city.
But for some reason there is term 六大都市 = 6 daitoshi and they are Tokyo, Osaka, Kyoto, Nagoya, Kobe and Yokohama.
Is there are any exact rules when city has right to be called 大都市 and when it is just 都市?
For example, how many 大都市 in Japan? Only 6 or more? What about Sapporo, is it daitoshi or just toshi?