Indispensable – अपरिहार्य, अनिवार्य, अत्यावश्यक

Adjective – If you say that someone or something is indispensable, you mean that they are absolutely essential and other people or things cannot function without them.

Example – A good dictionary is indispensable for learning a foreign language.

Synonyms – Basal, basic, cardinal, crucial, essential, fundamental, imperative, key, necessitous, needed, needful, prerequisite, primary, required, requisite, vital.