In fashion design, "boyfriend" is a style of women's clothing that draws heavily from corresponding men's garments. Boyfriend-style clothes are designed to be looser or boxier and tend to be oversized giving the appearance that one is wearing their boyfriend's clothing.
Blazers, however, are dressier than sportcoats but not as formal as suit jackets. Traditionally, a blazer is wool, blue with a pocket, and has distinct silver or gold buttons. However, this "tradition" has receded over time, with men opting for cotton varieties and blazers without the customary buttons.
