Millisecond (ms)
Definition: A millisecond is one thousandth of a second.
History/origin: The millisecond grew in importance with telegraphy, industrial control, computing, and modern user-interface timing.
Current use: Milliseconds are common in software performance, gaming latency, response times, and many industrial or medical devices.
Week (wk)
Definition: The week is a calendar interval of seven days, commonly used to group work, school, religious, and planning cycles.
History/origin: Seven-day cycles spread through ancient religious, astronomical, and civic traditions before becoming embedded in modern international calendars.
Current use: Wk is common in work schedules, class plans, sprint planning, pregnancy tracking, subscriptions, recurring chores, rent cycles, and short-term goals.