Please lock the door before you leave.

To secure something in place so that it cannot be opened or moved.
I will lock my bike to the rack.
She forgot to lock her car.
He needs to lock the safe.
lock the door
lock the window
lock the car
secure
fasten
seal
The storm locked us inside the house.

To prevent access or movement; to confine.
The dog was locked in the yard.
She locked the door before leaving.
They locked the gates at night.
lock the door
lock someone in
lock up
confine
secure
shut
Please lock the door when you leave.

To secure something with a device that prevents it from being opened.
Don't forget to lock your car.
She always locks her bike at the rack.
He locked the safe before leaving.
lock the door
lock the window
lock the gate
secure
fasten
seal
I need to find my house key to open the lock.

A device used to secure something, usually with a key or combination.
Please remember to lock the door when you leave.
He turned the lock to secure the gate.
She lost the key to her bike lock.
front door lock
padlock
deadbolt lock
fastener
bolt
latch