It varies from institution to institution, but generally the first number indicates the year you’re likely to study it, so “Psychology 101” is the first course you’re likely to study in your first year of a degree involving psychology, which is why it’s the introduction to the subject. The numbering gets messy for a variety of reasons.
I should point out I’m not an American university student, but this style of numbering system is becoming prevalent throughout the English-speaking world.
It varies from institution to institution, but generally the first number indicates the year you’re likely to study it, so “Psychology 101” is the first course you’re likely to study in your first year of a degree involving psychology, which is why it’s the introduction to the subject. The numbering gets messy for a variety of reasons.
I should point out I’m not an American university student, but this style of numbering system is becoming prevalent throughout the English-speaking world.