mainstay

Mainstay is a noun that denotes a person or thing acting as a principal support or indispensable element of a system, organization, or activity. In nautical usage, the term originally referred to a strong rope or chain that secures the main mast and helps stabilize the vessel’s rigging. Because of this stabilizing function, the word later acquired a broader metaphorical sense as anything that provides essential support.

Etymology: The word comes from Middle English mainstay, from main meaning "chief" and stay meaning "rope or pole." It was used in maritime writing from the 16th century and later extended into general usage to describe non-nautical forms of support.

Usage: Mainstay is commonly used to describe a person, organization, or thing that remains a reliable source of strength or stability. For example, a veteran employee can be described as a mainstay of the company, or a particular technology can be a mainstay of a production process. The plural is mainstays.

Notes: It is a straightforward, widely understood term that emphasizes central importance and reliability without connotations of fragility. It is often used in discussions of what underpins the performance of systems, communities, or economies.