1 ~ (for sb/sth) (to do sth) that is needed for a purpose or a reason
SYNESSENTIAL:
It may be necessary to buy a new one. * It doesn't seem necessary for us to meet. * Only use your car when absolutely necessary. * If necessary, you can contact me at home. * I'll make the necessary arrangements. * Changes can easily be made where necessary. * She has the qualities necessary to be a successful teacher.
2 [onlybeforenoun] (written) that must exist or happen and cannot be avoided:
This is a necessary consequence of progress.
IDIOMS
a necessary evil a thing that is bad or that you do not like but which you must accept for a particular reason:
The loss of jobs is regarded as a necessary evil in the fight against inflation.
