Emily Dickinson Lexicon

ES-SEN'TIAL, a. [L. essentialis.]

1. Necessary to the constitution or existence of a thing. Piety and good works are essential to the Christian character. Figure and extension are essential properties of bodies. And if each system in gradation roll, / Alike essential to the amazing whole. Pope.
2. Important in the highest degree. Judgment is more essential to a general than courage. Denham.
3. Pure; highly rectified. Essential oils are such as are drawn from plants by distillation in an alembic with water, as distinguished from empyreumatic oils, which are raised by a naked fire without water. Encyc.