yearslong

Yearslong is a compound adjective formed from the plural noun years and the adjective long, used to describe something that lasts for a substantial number of years. In English, the conventional hyphenated form years-long is standard when the phrase directly modifies a noun, as in a years-long project or a years-long conflict. Some writers also encounter the closed form yearslong, which is less widely accepted in formal style guides but appears in editorial practice and on the web.

Etymology and usage: The term derives from a straightforward combination of years and long, mirroring other duration expressions such as months-long or multi-year. The preference for hyphenation follows general rules for compound modifiers before nouns; the unhyphenated variant is more common in informal writing, headlines, or branding where space is limited, and in some dictionaries that list yearslong as an acceptable form.

Ambiguity and scope: Years-long denotes a duration extending over multiple calendar years, but it does not specify which years or how many, leaving the exact length context-dependent. It should not be confused with year-long (lasting exactly one year) or with multi-year (often used as a noun or adjective in corporate or research contexts).

Notable usage: While common in journalism and academic prose to emphasize prolonged activity, there is no single authoritative source naming yearslong as a distinct concept. It primarily functions as a descriptive stylistic variant rather than a technical term.

See also: year-long, multi-year, long-term.