essential

Needed so much that something cannot happen or succeed without it.

• Water is essential for life.
• A helmet is essential when you ride here.
• It is essential that everyone arrives on time.

How to use it: essential for something (Clean water is essential for health.); essential to something (Trust is essential to a strong friendship.); it is essential to do something (It is essential to check the brakes before leaving.)

Similar words: necessary, vital, indispensable

Opposites: unnecessary, optional

Common phrases: essential for something, essential equipment, absolutely essential

Very important or central to something.

• Music plays an essential role in the film.
• The garden is an essential part of the house’s charm.
• Her warmth was an essential element of her appeal.

Similar words: important, key, central

Opposites: unimportant

Common phrases: essential role, essential element, essential part

Belonging to the most basic nature or character of something.

• Its essential nature has not changed.
• The two stories share the same essential features.
• What is the essential difference between these approaches?

Similar words: fundamental, basic, underlying

Opposites: superficial

Common phrases: essential nature, essential character, essential difference

Describing a medical condition that has no known cause.

• The doctor diagnosed essential hypertension.
• Essential tremor can make writing difficult.
• She takes medication to control her essential tremor.

Similar words: idiopathic

Common phrases: essential hypertension, essential tremor, essential blepharospasm