"一日三餐" (yī rì sān cān) 用英语可以说作 "three meals a day" 或 "three squares a day". 这个短语指的是人们通常每天吃早饭、午饭和晚饭这三顿饭。

这个短语来源于人们在军队中吃饭的惯例。在军队中，士兵们会在每天的早晨、中午和晚上吃三顿饭。这个习惯渐渐地被人们接受，并且变成了人们每天都会吃三顿饭的惯例。

例句：

Eating three meals a day is important for maintaining a healthy diet.

I always make sure to have three squares a day to keep my energy levels up.

My grandmother says that she can't remember the last time she missed one of her three meals a day.