What is the difference in freshman, sophomore, junior and senior?

A student's year in high school or college is denoted by their status as a freshman (grade 9), sophomore (grade 10), junior (grade 11) or senior (grade 12). Likewise, a first-year college student is a freshman, while a student in his fourth year of college is referred to as a senior.

College-year rankings are sometimes calculated based on the number of college semester hours that the student has completed. For example, some colleges rank freshmen as students with fewer than 32 semester hours, while sophomores have less than 64 semester hours but more than 32. Under this system, juniors have at least 64 but not more than 96 semester hours, while seniors have at least 96.