In the Japanese tea ceremony, a very thick, concentrated form of matcha made to be rich and opaque (koicha).
茶道の席で、先生が濃茶を勧めてくれた。
At the tea ceremony, the teacher served koicha.
この茶室では濃茶（こいちゃ）とお薄の両方を出します。
This tearoom serves both koicha and usucha.