AT a class I took for SFI activists on May 29 on political economy, someone asked me the question: what is a derivative? My answer, I could feel, was unclear to the audience. Since other comrades too would be having this question in mind, I thought I should attempt, hopefully, a clearer answer here.A derivative is a contract through which the contracting parties trade in risk. The idea of a contract through which risk is traded is not a new one; indeed it is familiar to us all.