essential

Among the signature elements essential to the design are the contiguous oval shape and the gradual slope — also known as the rake — of the seating.

A better understanding of the processes involved in retaining water in the snow and the integration of dynamic parameters, such as changes in the altitude of the ice sheet, are essential to reduce uncertainties.

Katie Hagmann, the group's resources spokesperson, said a council tax increase was essential due to the "need to protect vital services".

Hope is often said to be the best medicine, essential to getting people through difficult times.

By 2010, economic globalization was cutting good-paying factory jobs here, income inequality was widening and corporate bailouts were booming — all essential ingredients for rising working-class resentment and deepening domestic divisions.