Sterility and infertility are often used interchangeably to refer to the inability to conceive after one year of unprotected sex. Specifically, sterility refers to the inability to produce offspring while infertility refers to an inability to conceive due to clinical issues or miscarriage after implantation. However, according to Professor CS Dawn, sterility and infertility essentially mean the same thing - an inability to conceive without contraception after a year of regular unprotected sex when the couple desires a child.