Introduction:
In English grammar, demonstrative pronouns are words used to point out or refer to specific people or things. They can be used to indicate proximity in time or space. One such demonstrative pronoun is "which," which is used to refer to a specific object or person in a sentence.

Explanation:
The sentence "is the computer which my cousin gifted me" contains the demonstrative pronoun "which." Let's break down the sentence and analyze the usage of the pronoun.

Identifying the Demonstrative Pronoun:
The demonstrative pronoun in the sentence is "which." It is used to refer to the computer that the cousin gifted. The word "which" is used to introduce a subordinate clause that provides additional information about the computer.

Function and Usage:
The pronoun "which" is used to connect the main clause ("is the computer") with the subordinate clause ("my cousin gifted me"). It helps to provide further details or clarification about the computer.

Indicating Specificity:
The use of the pronoun "which" indicates that the speaker is referring to a particular computer. It suggests that there may be other computers, but the one being referred to is the one gifted by the cousin.

Indicating Possession:
The pronoun "which" also indicates possession. It shows that the computer belongs to the speaker and was gifted by their cousin. The pronoun "my" before "cousin" further emphasizes ownership.

Conclusion:
In the sentence "is the computer which my cousin gifted me," the word "which" serves as a demonstrative pronoun. It points out a specific computer that was gifted by the speaker's cousin and indicates possession. Demonstrative pronouns play a crucial role in English grammar by providing clarity and specificity in referring to people or things.