Koicha and usucha are different ways of serving matcha. Even if the quantity used for the koicha is twice as much as that for usucha, the manufacture of the matcha is the same. The tea ceremony is more formal when serving koicha. Officially, a ceremony should offer koicha and usucha. We say that we "whisk"(tateru) the tea for usucha, while we "knead" it (neru) for koicha.
Koicha and usucha are different ways of serving matcha. Even if the quantity used for the koicha is twice as much as that for usucha, the manufacture of the matcha is the same. The tea ceremony is more formal when serving koicha. Officially, a ceremony should offer koicha and usucha. We say that we "whisk"(tateru) the tea for usucha, while we "knead" it (neru) for koicha.