What type of clause in necessary to the meaning of a sentence?

A restrictive clause is necessary to the meaning of a sentence. It provides essential information about the noun it modifies, helping to clarify or specify which person or thing is being referred to. Without this clause, the sentence would lose important meaning or context. For example, in "The book that you lent me was fascinating," the restrictive clause "that you lent me" specifies which book is being discussed.