Transitive verb

Transitive verbs are those that need an object to complete their meaning.
Example:
1. She loves this dog.
2. He teaches English.
3. I write a blog.

We cannot say:
1. She loves.
2. He teaches.
3. I write.

Transitive verbs usually have a passive form.
Example:
1. Active: A cat bit a mouse.
2. Passive: A mouse was bitten by a cat.

See Voice for more details.

Transitive verbs include phrasal verbs such as knock down. Let's see examples below:

Active voice: The boxer knocked down his opponent with a powerful punch.
Passive voice: The opponent was knocked down by the boxer’s powerful punch.

Active voice: The construction crew knocked down the old building to make way for a new one.
Passive voice: The old building was knocked down by the construction crew to make way for a new one.

Active voice: The storm knocked down several trees in the park.
Passive voice: Several trees in the park were knocked down by the storm.

Active voice: The car knocked down the pedestrian who was crossing the street.
Passive voice: The pedestrian who was crossing the street was knocked down by the car.

Contrast Intransitive verbs which have no object.
Example: He laughed.

For more information, see Intransitive verb and Verb patterns 1, and 11-20.