Both ‘which’ and ‘that’ can start clauses that modify nouns in a sentence. Use the word ‘which’ to provide more information about an already-identified noun. Use ‘that’ to restrict the noun to something more specific than what you have already identified. Nonrestrictive clauses begin with ‘which’ (i.e., they do not change the meaning of the noun), and restrictive clauses begin with ‘that’ (and do change the meaning of the noun).
A simple test tells you which one to use: if you can remove the clause and the sentence still retains some of the same meaning, use ‘which.’ If not, use ‘that.’
In the incorrect usage, the removal of the clause ‘which have udders’ alters the intended meaning of the noun (‘cattle’) that it modified. Note that, in the appropriate use of ‘which’ given below, the removal of the clause ‘which have large black eyebrows’ does not alter the meaning of the noun, ‘cow’s eyes.’
INCORRECT: Female cattle which have udders sometimes live on dairy farms to produce milk.
CORRECT: The cow’s eyes, which have large black eyebrows, appeared set in a very angry glare.
In this incorrect usage, the clause ‘that has been his home for years’ provides more information about the barn, but not to restrict its meaning. Note that if you remove the ‘that’ clause, it leaves you with ‘The cow’s barn flooded in a recent storm’ – a complete sentence on its own – so the author should have used ‘which’ instead of ‘that.’
In the correct usage below, the word ‘that’ restricts the noun ‘cows’ so that you mean only those cows with an ability to stand on their back hooves. You need the clause ‘that can stand on their back hooves’ to keep the sentence sensible, and so you should choose ‘that’ instead of ‘which.’
INCORRECT: The cow’s barn, that has been his home for years, flooded in a recent storm.
CORRECT: Cows that can stand on their back hooves do not appear often, and I have never seen one.
Learn helpful ways to remember when you should use the word ‘that’ instead of the word ‘which’ when you provide more information in a sentence.