1nec·es·sary 
/ˈnɛsəˌseri, Brit ˈnɛsəsri/ adjective
/ˈnɛsəˌseri, Brit ˈnɛsəsri/ adjective 1 [more necessary; most necessary] : so important that you must do it or have it : absolutely needed
▪ Is it really/absolutely necessary for me to have surgery? ▪ The threat of a thunderstorm made it necessary to cancel the picnic. ▪ It's not necessary to wear a tie. ▪ Food is necessary for life. ▪ We had all the necessary ingredients. ▪ Apply another coat of paint if necessary. [=if it is needed] ▪ Take as much time as necessary. [=as much time as you need] ▪ She took the medicine only when absolutely necessary. ▪ a medically necessary procedure 2 always used before a noun, formal : unable to be changed or avoided
▪ Higher prices are a necessary consequence of the company's new services. ▪ There is no necessary connection between what is legal and what is moral. [=what is legal does not always have to be moral and what is moral does not always have to be legal]
▪ Is it really/absolutely necessary for me to have surgery? ▪ The threat of a thunderstorm made it necessary to cancel the picnic. ▪ It's not necessary to wear a tie. ▪ Food is necessary for life. ▪ We had all the necessary ingredients. ▪ Apply another coat of paint if necessary. [=if it is needed] ▪ Take as much time as necessary. [=as much time as you need] ▪ She took the medicine only when absolutely necessary. ▪ a medically necessary procedure
▪ Higher prices are a necessary consequence of the company's new services. ▪ There is no necessary connection between what is legal and what is moral. [=what is legal does not always have to be moral and what is moral does not always have to be legal]
necessary evil — see 2evil
