Synonyms of the word

required

• v. simple past tense and past participle of require.
• adj. Necessary; obligatory; mandatory.

compulsory

• adj. Required; obligatory; mandatory.
• adj. Having the power of compulsion; constraining.
• n. Something that is compulsory or required.

mandatory

• adj. Obligatory; required or commanded by authority.
• adj. Of, being or relating to a mandate.
• n. (dated, rare) A person, organisation or state who receives a mandate; a mandatary.

necessary

• adj. Required, essential, whether logically inescapable or needed in order to achieve a desired result or avoid…
• adj. Unavoidable, inevitable.
• adj. (obsolete) Determined, involuntary: acting from compulsion rather than free will.
• n. (Britain, archaic euphemistic, usually with the definite article) A place to do the "necessary" business…

needed

• v. simple past tense and past participle of need.
• adj. Necessary; being required.

needful

• adj. Needed; necessary; mandatory; requisite; indispensible.
• n. Anything necessary or requisite.
• n. Ready money; wherewithal.

obligatory

• adj. Imposing obligation, morally or legally; binding.
• adj. Requiring a matter or obligation.

requisite

• adj. Essential, required, indispensable.
• n. An indispensable item; a requirement.