Why is a person who has Klinefelters syndrome (XXY) a male even though he has two X chromosomes in his cells?

A person with Klinefelter syndrome (XXY) is considered male because the presence of the Y chromosome determines male sex characteristics. The Y chromosome carries the SRY gene, which triggers the development of male gonads (testes) and the production of male hormones, primarily testosterone. Although they have an extra X chromosome, the presence of the Y chromosome is the key factor that leads to the male phenotype. Thus, individuals with Klinefelter syndrome typically have male physical traits but may experience some variations in sexual development and fertility.