Read the following:
The chair which has a broken leg has been removed from the room.
We know that an adjective always describes the quantity, quality, condition, and the number of the noun. Here which has a broken leg describes the condition of the noun chair. Moreover, it qualifies the antecedent as the chair and according to the rule it sits after the noun chair. So the clause which has a broken leg is an adjective clause.
An adjective clause is a group of words that has its subject and predicate and performs the function of an adjective.
As an adjective, the adjective clause qualifies a noun. An adjective clause always sits after the noun. Some relative pronouns are used in an adjective clause. These relative pronouns work in the form of subject, object, and possessive in the sentence.
An antecedent sits before an adjective clause. Generally, an adjective clause starts with relative pronoun who, which, that, whom, whose, of which, and with relative adverb why, where, when, how, etc. When any relative pronoun works as an object of an adjective clause and transitive verb, it can be omitted.
(1) Adjective clause with a relative pronoun as subject:
In this case the subjective form of the relative pronoun (who, which, that) works as subject to adjective clause,
(i) Jamal is a businessman who lives in Dhaka
(ii) They have bought a car that is made in Japan.
(2) Adjective clause with relative pronoun an object.
In this case, the objective case of the relative pronoun (whom, which, that) works as an object to an adjective clause and it sits before the subject of the adjective clause.
The boy whom we helped was very helpless.
The land which they bought was very costly.
(3) Adjective clause with a relative pronoun as the object of a preposition:
In this case, a relative pronoun works as an object of a preposition. The preposition and the objective form of relative pronoun sit before the subject of the adjective clause. Examples: (i) This is the boy about whom I told you.
(ii) The flat in which they live is very gorgeous.
(4) Adjective Clause with Relative Pronoun as Possessive
In this case, the possessive form of the relative pronoun (whose/of which) is used. The possessive form of relative pronoun sits after the noun used as antecedent. Examples: The boy whose pen was lost was poor. He has a house whose color is white.
(5) Adjective clause with a relative adverb:
In this case where, why, when, as, how, are used as a relative adverb in the adjective clause. These relative adverbs sit at the beginning of the adjective clause. Like relative pronoun, relative adverb qualifies the noun used as antecedent. I know the place where he lives
principal clause adjective clause There is no mother but loves her child.
(7) Adjective clause with "the same -— as/that".
In this case, as/that qualifies a noun used as antecedent.
The clause before "as/that" is the principal clause and the clause from "as/that" till the last of the sentence" is a subordinate adjective clause.
Example: This is the same book = Principal clause
as/that I lost = Adjective clause