Incapable of being dispensed with
Imposed on one by authority, command, or convention
Maybe it wasn't necessary to say anything.
Carmen filled out all the necessary paperwork and then settled down for a long wait.
It is necessary to protect life, liberty, and property.
It is never necessary to urge her to study.
Never would she have thought that a push up bra was necessary with ample firm breasts, but they swelled from the bra in a way that was smooth and attractive.