A relative pronoun is a small word that links two parts of a sentence into one complete idea. The most common Arabic relative pronouns are «الذي» (who/which, masculine singular), «التي» (who/which, feminine singular), «الذين» (who, masculine plural), and «اللواتي» (who, feminine plural).
Example: “I read the book that my grandfather gave me” — the word «الذي» connects “the book” to “my grandfather gave me,” making the meaning clear. Another example: “This is the teacher who taught me to read.”
Notice that a relative pronoun never stands alone — it always needs a following clause, called the “relative clause,” to complete its meaning.