a relative pronoun is a pronoun used to mark a relative clause and having the same refrent as the element of the main clause (usually a noun or a noun phrase )which the relative clause modifies..
An eg. in english word which in sentence ''this is the house which Rohan built'' .. here which Rohan built is relative clause modifying the noun house .. the relative oronoun which marks the relative clause and refers to the man being reffered..to in the main clause...it can be considered to provide a link between two sentence .. ''This is a house''and ''Rohan built a house'', where the house reffered to in each case is same....
In providing a link between a subordinate clause and a main clause a relative pronoun is similiar in function to a subordinate cunjunction..... unlike a conjunction , however , a relative pronoun does simply mark the subordinate clause but also plays the role of noun with that clause...for eg. in the relative clause which Rohan built written above , the pronoun which functions as the object of the verb built..compare this with ''Rohan built the house afer he married '' where the conjunctin after marks the subordinate clause after he married , but doesn't play the role of any noun within that clause...
the word subordinate means relative.....