three Rs

noun[plural only]3

1. •
   The basic education received in primary schools, especially (but not necessarily limited to) reading, writing and arithmetic.

   • Elementary schools have already done a noble work, but among many of them the demand has now arisen for something more than the three R’s and simple Bible-teaching. — 1908
2. •
   The basic precepts of any subject matter.

   • Chapter 11: The Big C and the Three Rs: Chores, Relaxation, Recreation, and Rebellion — 2002
3. •
   Reduce, reuse and recycle.