When the relative pronouns ‘who ", ‘which’ or ‘that’ (in object case) are omitted the relative clause becomes a contact clause.
We leave out the relative pronoun (who/which/that) if it is not the subject in the sentence.
- The book I gave you had many pictures.
- The book I am reading at the moment is very interesting.
- The town you live in is very old.
- The sweets I bought yesterday are delicious.
- The football match my friend played in was very exciting.