Can I say,

a. The farmer is ploughing the paddy field by using / with a cow.

b. The ox is ploughing the paddy field.

c. The cow is ploughing the paddy field.

d. The bull is ploughing on the paddy field.

e The bull is ploughing on the paddy.
Veteran Member7,791
a. The farmer is ploughing the paddy field by using / with a cow.

b/c/d/e. The ox/cow/bull is ploughing (on) the paddy (field). -- All permutations are OK I guess, but it would be usual to omit the word "on", and I prefer to write "paddy field" in full.
Veteran Member6,295
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Mr Wordy is absolutely right, but I just wanted to add an extra note about cow / ox / bull. In Britain (where I live), we usually only see cows (which is the name for the female animal) in the fields. Bulls (the name of the male animal) are much less common because they don't produce milk.

British people will often say "cow" without even thinking about whether they are talking about a male or female animal.

Most people in Britain know what an ox is, but the word is not used much - it has an old-fashioned feel, like something from the Bible or Shakespeare.

There's also the word "cattle", which farmers use to mean both male and female animals, but most people who aren't farmers will still just say "cows" to refer to a mixed group. Cattle itself is a plural word - if you are talking about one animal, you can't say "a cattle"; you could say "a head of cattle" but you'd be better off saying "cow" or "bull".

A "bovine" is another word for the same animal, but that sounds too scientific for everyday use.