Slacks are a type of pants, usually made from dressier fabric than jeans, that people wear for work, school, or more formal occasions. The word typically refers to trousers that are comfortable and slightly loose-fitting, but still look neat and professional. You might wear slacks to a job interview, a school concert, or a nice dinner, while you'd probably choose jeans for playing outside or doing yard work.

Today, slacks sit somewhere between casual jeans and dressy suit pants. They're the kind of pants that work well when you want to look put-together without being too stiff or formal.

Business people often wear slacks to the office. Students might wear them as part of a school uniform or for a debate competition. When someone says “business casual,” they usually mean slacks (not jeans) with a nice shirt. The term applies to pants for anyone, though you'll also hear people use more specific words like “dress pants” or “trousers” to mean the same thing.