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.
A habit is a learned behavior that a person repeats so often that he or she begins to do it without even thinking about it. Certain habits can be helpful, like the habit of brushing your teeth before going to bed or buckling your seatbelt when you get into a car.