Knock on door.

Meaning: This means to strike the surface of the door with a sharp blow to get someone's attention.

Choice of Words: Knock is a verb meaning to strike a surface, such as a door, with a sharp blow. On is a preposition indicating a relationship of contact between two things. Door is a movable structure used to open and close an entrance to a building or room.

Alternative Expressions

Knock on the door.

Meaning: This means to hit the door to make a sound so that someone inside can hear you and open it.

Choice of Words: Knock means to make a sound by hitting something. On is a preposition that indicates that something is in contact with another thing. Door is the thing that separates the inside of a room from the outside. When you put them together, "Knock on the door" is a clear instruction to make a sound on the door.

Use your knuckles to knock on the door.

Meaning: This means to hit the door with your knuckles to make a sound so that someone inside can hear you and open it.

Choice of Words: Use means to employ something. Knuckles are the hard parts of your fingers. Knock means to make a sound by hitting something. On is a preposition that indicates that something is in contact with another thing. Door is the thing that separates the inside of a room from the outside. When you put them together, "Use your knuckles to knock on the door" is a clear instruction to make a sound on the door using your knuckles.

Please knock on the door before entering.

Meaning: This means to ask someone to hit the door to make a sound before they go into a room.

Choice of Words: Please is a polite word that indicates a request. Knock means to make a sound by hitting something. On is a preposition that indicates that something is in contact with another thing. Door is the thing that separates the inside of a room from the outside. Before is a preposition that indicates that something happens prior to another thing. Entering means to go into a place. When you put them together, "Please knock on the door before entering" is a polite request to make a sound on the door before going into a room.

Related Expressions