Like relative adverbs, relative pronouns are also used to join two relative clauses. These relative clauses relate things, persons, or animals which are called antecedents.
Examples :– That, which, what, who, whom, whose. Further, by adding, ever, or soever to what, who, and which, many different forms can be created. Such as, whosoever, whichever, whatever, etc.
Clauses introduced by relative pronouns are called adjectives clause as these clauses function like adjectives.
•The pen which you gifted me, is now lost. (for thing)
•The lake, which we saw last time, is totally dried. (for thing)
•This is the bike that we used for riding. (for thing)
•I always remember the people who helped us in need. (for person)
•Equatorial forests, which are the storehouse of diverse species, are on the verge of degradation. (for thing)
•I saw a sensitive person who was serving selflessly for poor people. (for person)
•He is the man whose pocket was lost. (for person)
•You know the farmer whom we helped. (for person)
•There are a lot of animals which suffer from water scarcity in summer. (for animals)
•This is the bat that we purchased for tournament.(for thing)
•The same forms of relative pronouns are used to singular and plural, masculine and feminine.
For person, in the subjective or nominative case, that and who pronouns are used; whereas, in the possessive case only whose is preferred. Apart from this, in the objective case, whom or who along that is used.
•He is the man who was complaining. (subject)
•He is the man whose pocket was lost. (possessive)
•He is the man whom we saw begging. (object)
“What” pronoun is commonly used for things in all cases–subjective, objective ,and possessive.
“Which” pronoun is also commonly used for things and animals. Moreover, who, generally, used for person, but sometimes, it also preferred for animals.
•There are a lot of animals which suffer from water scarcity in summer.
Relative pronouns are also classified in restrictive and continuative forms.
In the restrictive form, the clause introduced by a relative pronouns describes the antecedents more specifically.
However, non-restrictive or continuative form does not describe the antecedents more clear manner.
•Equatorial forests, which are the storehouse of diverse species, are on the verge of degradation. Here, if we drop the relative clause, the meaning of the sentence will not change drastically.
In the restrictive form, comma is not essential, but in the non-restrictive form comma is essential before relative pronouns.
•The animal, which he likes, could not be found in the nearby forest.
•My dog, which I bought from a village, is no more now.
“That” as a relative pronouns, cannot be used in the non-restrictive relative clause. Most importantly, “which” relative pronoun is only used as a object of relative clause. But, “who and that” are used as both subject and object
Now, it is clear that the relative pronouns are too confusing to grasp due to its dynamic nature. I have tried my best to make it more simple for you. Hope, it will help you.