三只羊用英文怎么说为啥不加s

"三只羊"用英语是 "three sheep"。在英语中,当数词与名词搭配时,数词会根据名词的不同变化其形式,规则如下：

如果名词是可数名词且在单数形式下末尾有s,x,sh,ch,或o等字符,则在数词前加es,如:
"a bus" -> "two buses"
"a box" -> "three boxes"
"a dish" -> "four dishes"

如果名词是可数名词且在单数形式下末尾没有s,x,sh,ch,或o等字符,则在数词前加s,如:
"a book" -> "two books"
"a pen" -> "three pens"

如果名词是不可数名词,则不用加s,如:
"water" -> "two water"

综上所述,在英语中 sheep 是可数名词且单数形式末尾没有s,x,sh,ch,或o等字符,因此在数词前面加s，所以是 "three sheep" 。

例句:

The farmer had three sheep in his field.
(农民在他的田里有三只羊。)
I counted three sheep in the meadow.
(我在草地上数了三只羊。)
Three sheep were grazing in the pasture.
(三只羊在牧场上吃草。)