Three R's Definition
noun
Reading, writing, and arithmetic, considered as the fundamentals of elementary education.
American Heritage
Reading, writing, and arithmetic, regarded as the basic elementary studies and the fundamentals of an education.
Webster's New World
Common misspelling of three Rs.
Wiktionary
Origin of Three R's
From the phrase reading, 'riting, and 'rithmetic alteration of reading, writing, and arithmetic
From American Heritage Dictionary of the English Language, 5th Edition
