Something that is required or mandatory.

A legal requirement.

कानूनी आवश्यकताएँ

English Usage: It's obligatory to wear a seatbelt while driving.

Hindi Usage: गाड़ी चलाते समय सीट बेल्ट पहनना कानूनी आवश्यकताएँ है।

An organism that lives on or in a host and benefits at the host's expense.

A person who exploits others, especially in financial terms.

शोषक

English Usage: He is a parasite who takes advantage of his friends' generosity.

Hindi Usage: वह एक शोषक है जो अपने दोस्तों की उदारता का लाभ उठाता है।