I know it's a very basic question, and I've looked up the definition of "subject." This very question was asked within a linguistic course that I am taking, the answer to which is apparently rice (see the example sentence below). I am quite surprised by this answer, for I thought that the subject is that which acts, and the object is that which is acted upon. So the sentence 'Rice is being cooked by Mary', could always be restated as 'Mary is cooking rice', and surely here, Mary is the subject. Anyway, the reason provided as to why rice is apparently the subject is as follows:

"'Rice is the subject of this sentence. When you change the word rice into 'potatoes' the verb changes, but if you change 'Mary' into 'Mary and John', the verb does not change."

(a) Potatoes are being cooked by Mary

(b) Rice is being cooked by Mary and John

(Emphasis not my own)

I am also having a hard time understanding the connection between the significance of a change or lack thereof of the verb, and the identification of the subject within the given sentence.

  • 3
    The point of the passive voice is to make the active-voice object into the subject of a sentence. "Mary (S) is cooking rice (O)" becomes "Rice (S) is being cooked [by Mary]" Sep 7, 2016 at 18:05
  • @Andrew Leach: Wonderfully succinct! I'm not sure anyone here would be able to explain the relevant principle any better than that. I'd be just as happy to upvote your text as an Answer rather than a Comment, but let's see if it answers all OP's doubts. Sep 7, 2016 at 18:18
  • Take a look at this.
    – user33000
    Sep 7, 2016 at 18:20
  • 2
    Do not confuse the subject and the object of a sentence with the agent (also known as actor) and the patient. I tried to explain this point once in an overlooked answer of mine: ell.stackexchange.com/a/67582/3281. Sep 7, 2016 at 18:25
  • 1
    @DamkerngT. Hearty agreement that the agent/patient relationship lends real clarity to analysis of the passive voice. Your answer wasn't completely overlooked: I see an Alleluia there! Sep 7, 2016 at 19:23

3 Answers 3


I thought that the subject is that which acts, and the object is that which is acted upon.

This is often true in an active-voice sentence, but not in a passive-voice sentence.

That which acts/is acted upon and subject/object really describe two different categories, not a single category.

  • That which acts and that which is acted upon are semantic roles, the roles a word or phrase plays with respect to the meaning of an utterance. The usual terms in linguistics are Agent (actor) and Patient (acted upon).

  • Subject and Object are syntactic roles, the roles a word or phrase plays with respect to the structure of an utterance.

In an active-voice sentence the Subject is also the Agent, and if the verb is transitive the Patient is the Direct Object. (If the verb is intransitive there is neither an obect nor a patient.)

In a passive-voice sentence the Subject is the Patient; the Agent may be omitted or expressed as an Oblique, the complement of a preposition phrase with by.

A syntactic rule in English is that in a clause headed by a finite verb that verb must 'agree' with its Subject in person and number—that is, the number and person of the Subject contribute to determining what inflection the verb bears. The only distinctive inflections affected by this rule in contemporary English are the 3d person singular -s inflection with regular verbs, the have/has constrasts with HAVE, and the am/is/are and was/were contrasts with BE.

In the two sentences cited in your example, one sentence uses rice and is and the other uses potatoes and are. Otherwise the two sentences are identical. Rice is singular and potatoes is plural; that is the only difference which can account for the is/are contrast, so rice and potatoes must be the subjects of their respective sentences.

Actually, many sentences, such as those headed by "linking" verbs like be, become, seem, have no Agent or Patient—they present a different set of semantic roles—but that's not something we need to get into here.


Rice is being cooked (by Mary).

The right way to do this is by first eliminating the prepositional phrase which would be the "by Mary". Mary would be the object of the prep and not the subject. So by taking this out, you would be left with "Rice is being cooked". From here you can easily see what the subject is, rice. This is because Rice is doing the action of "cooked".

However, when you switch it up, Mary is cooking rice, you can see that Mary is now the subject because she is the one cooking rice, or doing the action. Rice would be the Direct Object in this case because that is what is being cooked. You can ask yourself, what is being cooked, and that is rice. Therefore, Rice would be the DO (but only in this case).

REMEMBER: The thing doing the action is almost always the subject


I am quite surprised by this answer, for I thought that the subject is that which acts, and the object is that which is acted upon.

"...subject is that which acts..."

Are the potatoes performing an action?

Is the rice performing an action?

What does the verb cook mean?

to undergo the action of being cooked --Webster's. Cook. v.

(a) Potatoes are being cooked by Mary.

Potatoes | are being cooked | by Mary

Subject | Present Progressive verb phrase | adverb prepositional phrase, acting as an adverb and is modifying the verb phrase to answer what an adverb would ask, "Who?" Who is cooking the potatoes? Mary.

(b) Rice is being cooked by Mary and John

Rice | is being cooked | by Mary and John

[again, same type of prep. phrase and modifying "is being cooked." This time the preposition "by" has a compound object: Mary and John.]

Here's the rule:

5c. The number of the subject is not changed by the phrase following the subject.

Remember that a verb agrees in number with its subject, not the object of the preposition. The subject is never part of a prepositional phrase.

John E. Warriner. Warriner’s English Grammar and Composition. Third Course. Liberty Edition. Orlando, Florida: Harcourt, Brace, and Jovanovich. 1986. 161.

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