essential

Essential is an adjective and a noun used to describe something that is absolutely necessary or fundamentally important. As an adjective, it refers to elements required for function or survival, such as water and shelter, or to core characteristics that define something, for example, “the essential qualities of a good leadership style.” It can also indicate importance in order or priority, as in essential tasks within a project. As a noun, essentials denotes basic necessities or the indispensable elements needed to live or complete a role, often phrased as “the essentials.”

Etymology traces essential to Latin essentialis, from essentia meaning essence, itself from esse, “to be.” The term conveys a sense of what is inherent or integral to a thing’s nature or operation.

Usage and nuance: essential is stronger than merely important, but its degree can vary by context. Some things are described as essential to a process, while others may be essential for health or safety. It is common in compound phrases such as essential to, essential for, and essential part. In specialized domains, the word appears in phrases like essential nutrients (nutrients the body cannot synthesize), essential amino acids, essential fatty acids, and essential oils.

Nonessential or non-essentials are terms used to denote items or elements not required, optional, or peripheral. The plural form essentials refers to a set of basic needs or fundamental items, such as “the travel essentials.” Related terms include essence and essentialism, which touch on the nature or philosophy of essence.