Bachelor
Definition 1 of 3
Pro Tip 1/3
Marital Status
Use 'bachelor' when discussing their marital status, not their personality or habits. Although he's quite the loner, calling him a bachelor simply highlights that he's unmarried.
Pro Tip 2/3
Not Gender Neutral
'Bachelor' refers only to men; for women, use 'bachelorette' or 'single woman'. My aunt is a bachelorette, similar to how my uncle was a bachelor before his marriage.
Pro Tip 3/3
Cultural Perception
The term may carry a cool, desirable image in some cultures but not in all. In some societies, being a 40-year-old bachelor is seen as admirable; in others, not so much.