We use contain to say that something has or holds things inside it. It means the thing is inside or part of another thing.
The box contains old books.
The bottle contains water.
Contain means to stop something bad from spreading or getting worse. It is often used for diseases, fires, or problems.
Firefighters contain the fire quickly.
They contain the disease in the city.
Contain can mean to keep feelings or emotions inside and not show them openly. It means controlling strong feelings.
He could not contain his excitement.
She contained her anger in the meeting.
In science, contain means to have a certain chemical or part inside. For example, food or drink can contain ingredients or chemicals.
This drink contains sugar.
The tablet contains vitamin C.
To contain something means to control or limit it, like a problem or action, so it does not get worse or grow bigger.
The government tried to contain the crisis.
She contains her spending carefully.
In technology, to contain means to have or store information or data inside a file, folder, or system.
The folder contains many files.
This program contains user data.
