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.
Synonym Discussion of vigorous. vigorous, energetic, strenuous, lusty, nervous mean having or showing great vitality and force. vigorous further implies showing no signs of depletion or diminishing of freshness or robustness as vigorous as a youth half his age.