Full-time describes work or activity that takes up someone's entire normal schedule, typically around 40 hours per week for adults or the complete school day for students. When someone works a full-time job, that job is their main focus and responsibility. A full-time teacher spends their weekdays in the classroom, planning lessons, and helping students. A full-time student attends all their classes and focuses on their education as their primary commitment.

The opposite is part-time, which means working or participating for fewer hours. Your parent might work full-time at an office while your older sibling works part-time at a restaurant on weekends. Some adults have two part-time jobs instead of one full-time job.

People also use the phrase more loosely to mean something takes up all of someone's attention and energy. A parent might joke that keeping track of a busy toddler is “a full-time job,” meaning it requires constant attention even though they aren't getting paid for it. When your friend trains intensely for competitive gymnastics, going to the gym every day after school, you might say gymnastics has become their full-time focus, even though they're still a student.