Defining clauses
the umbrella ... i bought last week is alredy broken
the umbrella THAT i bought last week is alredy broken
the woman ... visited me in the hospital was very kind
The woman WHO visited me in the hospital was very kind.
The people bought our house
They’re the people WHO/THAT bought our house
Some cells show abnormality.
Here are some cells WHICH/THAT show abnormality
She met the people at Jon's party
They’re the people WHO/THAT she met at Jon’s party