Roy comes from Old French roi, rei ('king'), from Latin rex (reg-) ('king'), from Proto-Indo-European *h₃rēǵs ('ruler, king'), from *h₃reǵ- ('to straighten, rule'). The historical chain includes Old French roi and Latin rex. Older glosses in the chain include "king", "ruler, king", and "to straighten, rule", which help explain the semantic range of the modern word. Morphologically, roy is best read as borrowing, yielding an English noun shaped by both form history and later usage. In current English it functions as a noun, with the sense "an archaic or dialectal word for a king". related forms include royal, regal, and rex. The result is an English noun whose etymology preserves the older forms while supporting the word's specialized modern meaning.