Is there a term for the part of a sentence that is in the form "Customers who ..." or "Products that ..."?

Solution 1:

Your question is somewhat misleading, and may contain a false assumption. A statement like the following:

Customers who have never paid a dime

is not a sentence. It's a noun phrase. Let's break that down:

Customers is a noun. Nouns are not inherently subjects or objects, so it's not correct to refer to this as either the subject or the object.

The remaining part who have never paid a dime is a relative clause, which is an embedded sentence that is used to modify something in the larger context. The subject of the embedded clause is the relative pronoun who, and the remainder have never paid a dime is the predicate of the relative clause.

However, using terms such as "predicate" and "relative clause" may be intimidating to people using your software. My best offering for newbie-friendly terminology would be:

• Call Customers a noun (most people at least know what that means)
• Call who a "question word", and make it clear by example what you're referring to
• Call have never paid a dime a "description"

Solution 2:

These are sentence fragments, not whole sentences here. You are actually only giving us the subject or object of a sentence, without the rest of the sentence to go around it. They are in fact all noun phrases using a relative clause:

[Customers [who [have never paid a dime]] should be shot.

The short answer to your question is that there isn't a grammatical term for "noun + relative pronoun", because we don't analyse sentences that way. That I know of, anyway: someone more knowledgeable than I is sure to punish me for that bit of hubris!

Solution 3:

I'm not sure entirely what you're looking for, but "customers who" is the (phrasal) subject of the sentence, and the rest is the predicate.

I don't know of a special word for noun + relative pronoun. Do you really think we need one?

Solution 4:

Actually, "Customers who have never paid a dime" is not a sentence; it is a noun phrase including a relative clause.

"Customers" is the simple noun. "Who have never paid a dime" is a clause which modifies the noun (customers). It is unnecessary to coin a term to describe the noun + the relative pronoun of the following clause, because they are not a single unit.

An example of a full sentence, using the relative clause (in italics):

Customers who have never paid a dime are detrimental to the business.