Lock the door please.

lock Noun

— A lock is a metal thing on a door (or on a window, drawer, etc.) that stops people from opening the door unless they have the right key to open it. No one will take things from my house. I have a very strong lock on the door. — A lock is two or more gates (doors) in water to let boats move from lower water to higher water or the other way.

lock Verb

— Someone locks a door when they close the lock with a key so that no one can come in. Remember to lock the door when you leave the house.

the Determiner

— Used, instead of a, to reference something specific, already known to exist. Compare "I read a book." and "I read the book." — Used with a stress, to show that the word following is special. Are you the John Smith that I went to school with? — Used with an adjective that acts like a noun to mean all of the people concerned The poor are always with us. — Used with superlatives forms of adjectives and adverbs. You are the best.

door Noun

— A piece of a wall that can be opened (leaving a hole in the wall to walk through) or closed (covering the hole). Some doors are on hinges; others slide. Please open the door for him. His hands are full.

please Interjection

— We say "please" when we want to ask someone politely to do something. Pass the salt, please.

please Verb

— Someone pleases someone else when they do what that person likes or wants. Giving her these flowers will please her.