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.
C2 needing or using a lot of physical or mental effort or energy: 1  He rarely does anything more strenuous than changing the channels on the television. 2  His doctor advised him not to do any strenuous exercise. 3  Strenuous efforts were made throughout the war to disguise the scale of civilian casualties.