Units?

<p>Hello! I'm Bart, I'm 17, I come from Poland and I want to study at an American college after I finish high school. I keep on getting more familiar with the American educational system, but there are still a few things that are unclear to me. When looking through college's profiles on collegeboard.com, I meet a concept "UNITS" in the High School Preparation table. What are those UNITS? And what does it mean, that some units of science must be lab? </p>

<p>Thank you,
Bart</p>

<p>A class that meets for a whole year is one unit. A science like Biology, Chemistry, or Physics normally includes some laboratories. Environmental Science, Astronomy, or Psychology might not.</p>

<p>Polish high school education lasts for 3 years, so it’s impossible to have 4 units of Math, but the amount of hours differs - I have 3 units of social studies, but only one hour a week and 3 units of math, but 5 hours a week. How can I show it to the university? It must be confirmed by somebody, right?</p>