1) Essential 2) Necessary 3) Necessity 4) Requirement 5) Requisite 6) Something wanted 7) Something wanted or needed 1) Need 
something which is greatly desired
• (n.) Anything desired; that of which the lack is felt; a want generally felt and acknowledge.
De·sid`e·ra'tum noun ; plural Desiderata . [ Latin , from desideratus , past participle See Desiderate .] Anything desired; that of which the lack is felt; a want generally felt and acknowledge. 
Desideratum is Latin for something lacking; something missing
[n] - something desired as a necessity
desideratum (singular) What is desired but not yet on hand.
noun something desired as a necessity; `the desiderata for a vacation are time and money`
something wanted or needed.