What Are Compound Subjects & Predicates?
English sentence structure allows for both compound subjects -- more than one subject described by a single predicate -- and also for compound predicates, in which multiple predicates refer to one or more subjects. Since compound subjects may contain both single and plural forms, some variations in subject-verb agreement may occur in these sentences.
1 Subjects and Predicates
The subject of a sentence can be a noun (common or proper) or pronoun: "Mary went shopping;" "She bought milk." The subject designates the main focus of the sentence and the performer of actions described by its predicate. The predicate consists of a verb and all elements associated with it, such as prepositional phrases, adjective phrases and adverbs: "Juan took an advanced math class;" "Sharon was glad to see her mother." The predicate comments on and completes the subject.
2 Compound Subjects
A subject may be expressed by multiple nouns connected by the conjunctions "and" and "or:" "Steve and Mary went to dinner at a fine restaurant;" "Either Miko or Sachiko wrote the letter;" "John, Peter and Aaron play varsity football." In these sentences, the verb expressed by the predicate applies to all members of the subject.
3 Compound Predicates
Compound predicates can apply to simple and compound subjects: "Rachel washed the dishes and went to bed," "Rachel and her sisters cleaned the kitchen and put everything away." Elements of a compound predicate can be joined by the conjunctions "and," "or" and "but:" "Jackie registered for the class but dropped it;" "Claire got up early and went for a run."
4 Compound Subject-Verb Agreement
When compound subjects contain both a singular and a plural element joined by "and," present tense verbs are plural: "Anna and Mary study Spanish together." But when compound subjects are joined by "or/nor," rules of agreement state that a present-tense verb in the predicate must agree with the element closest to the verb: "Either the counselor or the campers take a hike every morning." "Neither the students nor the teacher has a calculator handy."