indispensable
//ˌɪndɪˈspɛnsəbəl//
Adjective
indispensableCanonical form
1
Absolutely necessary or essential; impossible to do without.
Water is indispensable for life.
2
Of a person: too important or valuable to be replaced or removed.
She has become indispensable to the team.
Antonym
Noun
indispensableSingular
indispensablesPlural
1
A person or thing that is absolutely necessary.
A good dictionary is an indispensable for language learners.