AM and PM are associated with 12-hour timekeeping, as opposed to the international 24-hour clock. The 12-hour system grew up mainly in Northern Europe, and spread globally from there via the British Empire.
The adjective STRENUOUS has 2 senses: 1. characterized by or performed with much energy or force. 2. taxing to the utmost; testing powers of endurance. Familiarity information: STRENUOUS used as an adjective is rare.
verb (used with object) 1. to put forth or into use, as power; exercise, as ability or influence; put into vigorous action: to exert every effort. 2. to put (oneself) into strenuous, vigorous action or effort.