A relative pronoun is a pronoun which refers or relates to some noun preceding it e.g., if we say

• This is Muhammad who has passed هَذَا مُحَمَّدٌ الَّذِي نَجَحَ

• This is a door which is in front of the mosque هَذَا بَابٌ الَّذِي أمَامَ الْمَسْجِدِ ,

• This is a cat that has sat هَذَا قِطٌّ الَّذِي جَلَسَ

 In the above sentences the nouns Muhammad, door and cat are called Antecedents and the words who, which and that refer to them respectively. In Arabic however all these three words (who, which and that) are represented by a single word الَّذِي

Translation	Transliteration	الإسِمُ الْمَوْصُوْلُ
Allah who has created humans	Allah al-lazi khalaq al insaan	اللهُ الَّذِي خَلَقَ الإنْسَانَ
The student who is in a school	At-talibu al-lazi fi madrasatin	الْطَّالِبُ الَّذِي فِي مَدْرَسَةٍ