Prepositions are words that indicate the relationships between various elements within a sentence. In formal English, prepositions are almost always followed by objects.
e.g. The policeman shot (verb) the man (object) with (preposition identifying the man being shot) a knife.
e.g. I put (verb) the pen (direct object) on (preposition indicating the position of the pen) the table (indirect object).
e.g. I put (verb) the pen (direct object) under (preposition indicating the position of the pen) the table (indirect object)
Prepositional phrases always consist of the object and the preposition. Prepositional phrases can act as adjectives or adverbs. When they are used as adjectives, they modify nouns and pronouns in the same way single-word adjectives do. When prepositional phrases are used as adverbs, they also act in the same way single-word adverbs and adverb clauses do, modifying adjectives, verbs, and other adverbs.
Prepositional words and phrases are difficult, especially for ESL learners, because different prepositions may impart different meanings to the prepositional words and phrases. Even the same preposition may have different meanings to the same verb.
Catch on: understand.
e.g. The technology is fairly simple; before long, you'll catch on.
Catch up with: keep pace with.
e.g. Hurry up! You have to catch up with them; they’re well ahead of you.
Knock one’s head against a brick wall: become very frustrated.
e.g. Throughout his career, he had knocked his head against a brick wall several times.
Knock back a drink: consume a drink.
e.g. She decided to knock back a brandy in front of her parents.
Knock it off: shut up!
e.g. Will you knock it off? I’m on the phone.
Knock off: stop working; finish something quickly.
e.g. I knock off work at seven every day.
e.g. I knocked two books off within an hour.
Knock out: do something with great effort and energy.
e.g. I knocked myself out to do this project for you.
Knock over: steal (slang).
Knock someone over: surprise or shock.
e.g. His abominable behavior knocked everyone over.
Knock one’s knees together: be very frightened.
e.g. I knocked my knees together when I had to walk through that neighborhood.
Copyright© by Stephen Lau