ADJECTIVE /RELATIVE CLAUSE  a relative clause is a dependent or subordinate clause WHICH Qualifies or adds to the meanings of a noun or pronoun in the principal clause .For instance.The boy who met met with an accident is safe now. In this clause -The boy is safe now is main clause who met with an accident is a relative clause adding to the meaning of a noun  The boy.All that glitters is not gold. In this clause-All is  not gold is main clause -that glitters is adjective clause qualifying the pronoun-All .A RELATIVE CLAUSE  ANSWERS THE QUESTION WHO/?A RELATIVE CLAUSE IS INTRODUCED BY THE FOLLOWING; A relative Pronoun [ who,when, which, that,whose]For example ;I heard a song which was sweet  and melodious. Do you remember the occasion when Dad fell into the river .WHY CAN ALSO BE USED LIKE A RELATIVE PRONOUN AFTER REASON.For instance; Give me three reasons why you can't have dinner with me. Another introducer is;RELATIVE ADVERB[where,why,whence,how]FOR EXAMPLE;Tell me the place where you were born.BUT as a relative pronoun when it is followed by NOT.See the example;There was none but did not feel sad.[who did not feel sad] THAN AS A PREPOSITION BE
FORE. A RELATIVE PRONOUN.Take the example;This was a deed than which no nobler was done.SUCH and SAME followed by ,AS .FOR INSTANCE;Such boys as obey their parents are getting less.RELATIVE CLAUSES ARE OF TWO KINDS;DEFINING or RESTRICTIVE CLAUSES and NON DEFINING or NON- RESTRICTIVE CLAUSES.   THE DEFINING CLAUSE IDENTIFY or DESCRIBE a person or thing which may be a noun a pronoun in the main clause.They are introduced by the relative pronoun WHO,WHOM, WHICH, THAT, which refer back to the noun or pronoun.FOR EXAMPLE; Is that the waitress who served us.