它是大的用英文怎么说

"It is big" 的英语表达是 "It is large."

"Large" 是英语中形容物体大小的常用形容词，来源于中古英语中的 "lārge"，意思是"大的"。

例句：

The house is large. (这房子很大。)
The elephant is large. (这头大象很大。)
He has a large family. (他有一个大家庭。)