ox、bull、cow与buffalo这些名词均有“牛”之意。
ox : 泛指野生或驯养的牛类，系动物学的用词，通称，也指公牛。
We must lead an ox by the halter.
牵牛要牵牛鼻子。
Fierce-browed, I coolly defy a thousand pointing fingers; headbowed, like a willing ox I serve the children.
横眉冷对千夫指，俯首甘为孺子牛。
bull : 指未经阉割，通常用于配种的公牛，也指西班牙或美洲经专门饲料用作斗牛表演的公牛。引申指彪形大汉。
They did not see the sign by the gate saying "Beware of the bull".
他们没有看见门旁边“当心公牛”的警示。
This bull gores people.
这牛爱顶人。
cow : 指任何品种的成年母牛或乳用的乳牛。
He kept a few dairy cows.
他养了几头奶牛。
buffalo : 指水牛，在美国指野牛。
A cluster of vultures crouched on the carcass of a dead buffalo.
一群秃鹫蹲伏在一具野牛的尸体上。
Once there were 70 million buffalo on the plains.
北美大平原上曾有过7,000万头野牛。
Asian buffalo isn't as wild as that of america's.
亚洲水牛比美国水牛温顺些。