|In the sentences below, the compound subjects are indicated in boldface.
In grammar, a compound subject is a type of subject where two or more individual noun phrases are coordinated to form a single, larger noun phrase. Compound subjects cause many difficulties in the proper usage of grammatical agreement between the subject and other entities (verbs, pronouns, etc.). In reality, these issues are not specific to compound subjects as such, coming up equally as well with compound noun phrases of all sorts; but the problems are most acute with compound subjects because of the large number of types of agreement occurring with such subjects.
As shown in the examples, for English compound subjects joined by and, the agreement rules are generally unambiguous, but sometimes tricky. For example, the compound subject you and I is treated equivalently to we, taking appropriate pronominal agreement ("our car", not "your car", "their car", etc.). In languages with more extensive subject-verb agreement (e.g. Spanish or Arabic), the verb agreement is clearly revealed as also being first-person plural.
For the subjects joined by or, however, the rules are often ill-defined, especially when two elements that differ in grammatical gender or grammatical number are coordinate. (The tendency, in such cases, is to rewrite the sentences to avoid the conjunction: e.g. "Sylvia and I each have our own car, and one of us is planning to sell their car". Note that this still has a compound subject using and as the conjunction, and uses "semi-informal" "generic their" to get around the "his or her" problem. This could be avoided with a further rewrite: "Either Sylvia will sell her car, or I will sell mine."
Additional concerns appear in compound subjects in languages other than English. In many European languages, for example, a standard problem occurs with mixed-gender compound subjects. This problem does not appear in English, because they is genderless. But e.g. French has masculine ils vs. feminine elles; Spanish similarly has masculine ellos vs. feminine ellas. In addition, Arabic has gender as well as person and number agreement on its verbs, and more specifically in its literary language and in the more conservative spoken varieties, there is gender agreement with third-person plural subjects.
In addition, some languages allow subjects to follow verbs: either optionally for stylistic reasons, as in German, Latin or occasionally in English ("Now are entering John, Jim, and their wives"); as the normal state of affairs, as in Classical Arabic and Irish, where subjects precede the verb only for stylistic reasons; or even as a mandatory requirement, in languages with V-S-O or V-O-S word order and a strongly fixed word order. These languages often use different strategies for handling subjects after vs. before the verb: for example, tending to prefer an "agree with the closest phrase" strategy with a following subject, for pragmatic reasons, even when an "agree with the whole" strategy is used in other circumstances.
Multiple strategies have been used to handle both compound subjects in general and category disagreement between/among the coordinate members of the subject. Languages often differ in which strategies they use. Among the strategies are:
- General agreement: Consider the total set of entities involved, work out their properties, and assign a pronoun accordingly. (E.g. if the set of entities includes two women referred to in the third person, and the language has grammatical dual, as in Arabic, then the group's properties would be "dual number, female, third person", with corresponding pronoun humatā.)
- Closest agreement: Simply agree with the constituent noun phrase that is closest to the verb, and ignore the rest. This generally applies only to subject-verb agreement; pronominal agreement is by its nature long-distance, and so the concept of "closest" makes less sense in this case.
- If using "general agreement" and there is a disagreement among properties (e.g. some male, some female), either:
- Choose one (the traditional rule for most languages was to treat mixed groups as male; some modern rules, on the other hand, call for randomly choosing one sex or the other, or alternating choosing male and female in successive similar circumstances, or even for simply choosing the female gender in all cases).
- Use a construction (e.g. "he or she", "his or her", "our(s)") that captures both or all values of the disagreeing property. Often this is considered awkward and to be avoided.
Additional concerns in English
An additional concern in English is that there are special rules for pronouns in compound subjects. Although English has morphological case distinctions in pronouns (e.g. I vs. me), grammatical case is not a living characteristic of the spoken language, and hence the case-based terms subjective case (e.g. for I) vs. objective case (e.g. for me) are misleading. In general, in the spoken language, me is the default form, but I for an argument of a verb when occurring directly before a finite verb. On the other hand, in compound subjects in informal speech, me occurs in this position, e.g. Johnny and me are coming tomorrow (possibly because of the lack of direct agreement between me and are).
Children are never taught in school that they should always order oneself after any others in a compound subject and use I, saying Johnny and I instead of me and Johnny. Although intended specifically for compound subjects, when adopted by speakers it typically is generalized to compound objects, leading to alternations such as between me and you vs. between you and I.
- Everaert, M.; van Riemsdijk, H.; Goedemans, R. (eds) 2006. The Blackwell companion to syntax, Volumes I–V, Blackwell, London.
- Halliday, M.A.K & Matthiessen, Christian M. I. M (2004). Subject, actor, theme in An introduction to functional grammar. Hodder Arnold, London, England.
- Huddleston, R.; Pullum, K. (2005). A student's introduction to English grammar. Cambridge University Press.