What group of words contains either a subject or predicate but not both?

The group of words that contains either a subject or a predicate but not both is called a phrase.

Here's why:

* Subject: The subject of a sentence is the noun or pronoun that performs the action or is described by the predicate.

* Predicate: The predicate of a sentence includes the verb and everything that follows it, describing the action or state of the subject.

Phrases are groups of related words that do not contain both a subject and a predicate. They can be:

* Noun phrases: "The big red ball" (contains a noun, but no verb)

* Verb phrases: "Running down the street" (contains a verb, but no noun performing the action)

* Prepositional phrases: "Under the table" (contains a preposition, but no subject or verb)

Let me know if you'd like more examples!