Synonyms of the word

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…

essential

• adj. Necessary.
• adj. Very important; of high importance.
• adj. (biology) necessary for survival but not synthesized by the organism, thus needing to be ingested.
• adj. Being in the basic form; showing its essence.
• adj. Really existing; existent.
• adj. (of a lamination of a 3-manifold) Such that each complementary region is irreducible, the boundary of…
• adj. (medicine) Idiopathic.
• n. A necessary ingredient.
• n. A fundamental ingredient.

incumbent

• adj. Imposed on someone as an obligation, especially due to one's office.
• adj. Lying; resting; reclining; recumbent.
• adj. Prevalent, prevailing, predominant.
• adj. (botany, geology) Resting on something else; in botany, said of anthers when lying on the inner side of…
• adj. (zoology) Bent downwards so that the ends touch, or rest on, something else.
• adj. Being the current holder of an office or a title.
• n. The current holder of an office, such as ecclesiastical benefice or an elected office.
• n. (business) A holder of a position as supplier to a market or market segment that allows the holder to…

indispensable

• adj. (ecclesiastical, obsolete) Not admitting ecclesiastical dispensation; not subject to release or exemption;…
• adj. (of duties, rules etc.) Unbendable, that cannot be set aside or ignored.
• adj. Absolutely necessary or requisite; that one cannot do without.
• n. A thing that is not dispensable; a necessity.
• n. (in the plural, colloquial, dated) Trousers.

inevitable

• adj. Impossible to avoid or prevent.
• adj. Predictable, or always happening.
• n. Something that is predictable, necessary, or cannot be avoided.

necessity

• n. The quality or state of being necessary, unavoidable, or absolutely requisite.
• n. The condition of being needy; desperate need; lack.
• n. Something necessary; a requisite; something indispensable.
• n. Something which makes an act or an event unavoidable; an irresistible force; overruling power.
• n. The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual,…
• n. (law) Greater utilitarian good; used in justification of a criminal act.
• n. (law, in the plural) Indispensable requirements (of life).

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.

required

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

requirement

• n. A necessity or prerequisite; something required or obligatory. Its adpositions are generally of in relation…
• n. Something asked.
• n. (engineering) A statement (in domain specific terms) which specifies a verifiable constraint on an implementation…

requisite

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

thing

• n. That which is considered to exist as a separate entity, object, quality or concept.
• n. A word, symbol, sign, or other referent that can be used to refer to any entity.
• n. An individual object or distinct entity.
• n. (informal) Something that is normal or generally recognised.
• n. (law).
• n. (somewhat dated) The latest fad or fashion.
• n. (in the plural) Clothes, possessions or equipment.
• n. (informal) A unit or container, usually containing edible goods.
• n. (informal) A problem, dilemma, or complicating factor.
• n. (slang) A penis.
• n. A living being or creature.
• n. That which matters; the crux.
• n. Used after a noun to refer dismissively to the situation surrounding the noun's referent.
• n. (informal) That which is favoured; personal preference. (Used in possessive constructions.).
• n. (chiefly historical) A public assembly or judicial council in a Germanic country.
• v. (rare) To express as a thing; to reify.