Staid (adjective)

Not changing; remaining in a steady state; settled.

Origin:

Middle english, from old english stæðe "firm, stationary".

Examples:

1. The staid old bank was slowly being replaced by a sleek, modern skyscraper.
2. The staid atmosphere of the library was disrupted by a group of loud students.
3. The staid couple was content to live a quiet life in the suburbs.
4. He was known for his staid, conservative approach to business.
5. Despite her staid exterior, she had a wild side that only her closest friends knew about.