What are the three types of unemployment in U.S. economics?

I actually learned four:

• frictional
• structural
• cyclical
• seasonal

Seasonal is also part of frictional. That is just the changes in the market. People switch jobs or take a break or their contract is up. Construction workers, landscapers or any 'job' service falls in this category. Entertainers are faced with frictional unemployment all the time.(That is considered to be seasonal)

Seasonal is part of frictional, but frictional is not necessarily seasonal. Also, seasonal is predictable, frictional isn't always.

Ah, yeah, four is right. I was thinking three that occur when the economy is normal. And Times2's right about the difference. They're similar but the reason for unemployment is different.