Absence of the Feminine

A bachelor is usually thought of as an unmarried man who lives alone. 

The word can be traced to the Anglo-Norman bacheler, "knight bachelor," a young squire in training, the lowest stage of knighthood; it can also refer to the holder of a "bachelor's degree" from a four-year college or university.

But while the etymological essence of a bachelor might be a trainee, we must not forget the importance of  absence in defining a bachelor, the absence of partnership with the feminine.