longstanding
adj.adj. existing or continuing for a long time. You use this to describe relationships, problems, or traditions that have been around for many years.
adj. having existed or persisted over a significant duration. Often used to describe established relationships, disputes, or institutional practices.
The two countries have a longstanding agreement.
The company finally resolved a longstanding dispute with its former employees regarding pension contributions.
Despite recent changes in leadership, the university maintains its longstanding commitment to providing scholarships for students from underprivileged backgrounds.
Typically used attributively before the noun it modifies.
a long standing traditiona longstanding traditionWhile 'long-standing' with a hyphen is also correct, writing it as two separate words without a hyphen is generally considered a spelling error when used as an adjective.