What is the difference between cows and cattle?

Cattle is plural and generally refers to the bovine species as a whole. The term isn't gender specific, so cattle could refer to a bunch of bulls (males), a bunch of cows (females), or a mixture of both.

A cow is a single bovine female.

Cow
The mature female of cattle of the genus Bos.
The mature female of other large animals, such as whales, elephants, or moose.
A domesticated bovine of either sex or any age.

Cattle
Any of various chiefly domesticated mammals of the genus Bos, including cows, steers, bulls, and oxen, often raised for meat and dairy products.
Humans, especially when viewed contemptuously or as a mob.

Bovine
Of, relating to, or resembling a ruminant mammal of the genus Bos, such as an ox, cow, or buffalo.
Sluggish, dull, and stolid.

http://dictionary.reference.com/

Cows are female cattle and cattle is the whole herd.

cat·tle n.

1. Any of various chiefly domesticated mammals of the genus Bos, including cows, steers, bulls, and oxen, often raised for meat and dairy products.

2. Humans, especially when viewed contemptuously or as a mob.



cow n.

1. The mature female of cattle of the genus Bos.
2. The mature female of other large animals, such as whales, elephants, or moose.
3. A domesticated bovine of either sex or any age.


The last definition of cow is a "general usage" term. This is not a "proper" definition. Just as "ain't" is in the dictionary yet follows no rules of the language beyond accepted usage.


Dictionary.com

French has laid-down rules (by the Academie), which most French speakers ignore in everyday use. English has no laid-down rules. Any grammar book, or Plain English and so on are merely descriptive rather than prescriptive. (Similarly in English law, the Common Law section has no laid-down rules, but is the result of centuries of doing it that way. Unlike Statute Law, which is laid down by Parliament. They haven't decided to lay down the law about language - yet.)

follows no "rules" of the English......

.....follows no "rules" of the language......

Ya see! I can not even follow the rules!