The contemporary definition of the word yoga in India is "union with God." To a philosopher this is an unsatisfactory one. For originally the word, when split into its syllables ya and gam, meant "the way to go." Later it came to mean "the way to perfection." But in both cases the application of this term was not limited to God as a goal, although He was a common one. For there were materialistic, mental, religious, and philosophic yogas: indeed one could be an atheist and still pursue a particular yoga. The correct interpretation of the word indicates therefore that there is a carelessness and looseness in its use, on the one hand, and a radical misunderstanding of its right meaning, on the other.
-- Notebooks Category 4: Elementary Meditation > Chapter 1: Preparatory > # 116