indispensableadjective
US /ˌɪndɪˈspensəbəl/
too important or necessary to be without
“Happily unconscious of the new calamity at home, Miss Pross threaded her way along the narrow streets and crossed the river by the bridge of the Pont-Neuf, reckoning in her mind the number of indispensable purchases she had to make.”
✓ Engvera
