strict
Following rules very carefully, with little flexibility.
Strict means following rules carefully and enforcing them firmly, without much room for flexibility or exceptions. A strict teacher expects students to arrive on time, complete assignments properly, and follow classroom rules exactly. A strict coach might require the team to run extra laps if anyone shows up late to practice.
Strict people set clear expectations and hold others accountable. This isn't the same as being mean or unfair. In fact, many strict teachers and parents are warm and caring, but they believe that consistent rules help people learn discipline and responsibility. A strict piano teacher might insist you practice scales every day, not to be difficult, but because she knows that's how you'll improve.
The word can also describe rules themselves. A strict deadline means the work must be finished by a specific time, no exceptions. Strict instructions mean you need to follow them precisely, without improvising or taking shortcuts.
Some people thrive under strict guidance because they know exactly what's expected. Others find strict environments too rigid. When a friend follows a strict schedule for homework, they're being disciplined about when and how they study.