custom

吹灭生日蛋糕上的蜡烛是一种习俗。

It is a ___custom to blow out candles on a birthday cake.

在我国，结婚穿白色是一种习俗。

In my country, it's the ___custom to get married in white.

新娘穿白色婚纱是一种习俗。

It is a ___custom for the bride to wear a white wedding dress.