This is a sentence in my grammar book.

He was asked to write the letter.

In the book it says :
He = subject , was asked to write the letter = subject complement.
The verb ask is a catenative verb.(this part wasn't written, I added myself)

And I came across the following two sentences:

The medicine is not warranted to treat a patient's condition.

In this sentence ,I guess the same rule applies,
with to treat a patient's condition being a subject complement,
And verb warrant here is being used as a catenative verb.
Is my understanding right?

A business plan was designed to boost company's revenue.

However,in this sentence,
I am not sure if the infinitive to boost company's revenue can also be a subject complement,
as it seem to be a purpose adjunct, and verb design isn't catenative.
If my understanding is correct, how can the structure of this sentence be explained?

3 Answers 3


If I was to rewrite the second example so it followed the structure of the first, it might be:

The patient's condition did not warrant treatment by the medicine.

"Warrant" can be a verb, but in your second example it is a noun - justification or authority for an action, belief, or feeling. As such, it should not really be compared to your original example.

The structure of your final example is not the same as your first either, but if we rewrite it this way:

The company designed a plan to boost their revenue.

"Designed" is now the verb and "to boost" is catenative.

  • I don't follow how warrant (or warranted as written) in this context can be designated as a noun. Commented Apr 5, 2019 at 14:04

In this sentence:

He was asked to write the letter.


The active voice sentence would be:

His boss asked him to write the letter."

What happens is that the Indirect Object has become the Subject in the passive voice sentence. Therefore, "he" is used instead of writing "him" in the new sentence because object pronouns do not work as subjects.


The sentence:

A business plan was designed to boost company's revenue.

is similar to the first one. It is in the passive voice. "Was" is only expressing the time of action (design), and the number of the subject (singular). On the other hand, the infinitive phrase "to boost company's revenue" is acting as an adverb meaning "in order to" showing a reason for the designing of the plan. You can identify that by asking yourself the question: "Why did they design a business plan?" And the answer would be: "They designed the plan in order to (or simply to)boost..."

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