Englishfor English speakers
in
Preposition
—
Used to show that something is inside something else.
The cat is in the box.
—
Used to show that someone is at home, or is available.
Is John in?
The Doctor is now in.
—
Used to show movement towards the inside.
The rain came in through the window.
lifetime
Noun
—
A lifetime is the duration of the life of someone or something.