essential
es-sen-tial
adjective
Absolutely necessary or important; fundamental for existence or success.
"A good breakfast is essential for a productive day."
noun
A fundamental or necessary item; a basic requirement or element.
"Remember to pack all the travel essentials."
Thesaurus
Synonyms: necessary, indispensable, all-important, important, of import, all important, crucial, of the essence, constitutive, life-sustaining, substantial, vital
Antonyms: adjective, inessential, nonessential, procedural, unessential