worry and worry about

Question

I learned the word worry contains two functions: one is as a transitive verb and the other is an intransitive verb.

However, in this two sentences, (from TOEFL)

1. People have a variety of factors in their lives that cause them to worry, such as school, jobs, and personal relationships.

2. Even during times when I was not actually studying, I found myself worrying about the tests and I was unable to completely relax.

I thought worry is a transitive verb, it must not go with preposition, such as about, whereas as an intransitive verb, it should involve preposition.

And I thought the worry in the first sentence is a transitive verb because it has object; a variety of factors in their lives. Thus, I agree with this sentence has no preposition.

However, in second sentence, I thought worry is a transitive verb since it has object: the test. Then why preposition about is there if worry in that sentence is a transitive?

Or does this word function as an intransitive verb? if so, why an object the test is there?

Answer 1

It seems that nobody is going to answer, so let me try. It's a bit difficult too for me to understand the difference but let me simplify your example.

I think that we can represent the same meaning with two different structures.

(1) The future worries me

(2) I worry about the future

According to Cambridge Dictionary

In the first case, we got

worry [TRANSITIVE]

to make someone feel unhappy and frightened because of problems or unpleasant things that might happen

In the second case, we got

worry [INTRANSITIVE]

to think about problems or unpleasant things that might happen in a way that makes you feel unhappy and frightened

Let's take a look at Oxford Dictionary

Feel or cause to feel anxious or troubled about actual or potential problems.

[no object] he worried about his soldier sons in the war

[with object] there was no need to worry her

Feel [INTRANSITIVE]

Cause to feel [TRANSITIVE]

---

Knowing all this, let's return to your example

People have a variety of factors in their lives that cause them to worry

[Simplifying] A variety of factors worry them. [TRANSITIVE]

I found myself worrying about the tests

[Simplifiying] I worry about the test [INTRANSITIVE]

about the test is NOT the object, it is a prepositional-clause.