As a measure, fertility rate is the number of children born per couple, or person or population. This is different to fecundity. This is defined as the "potential" for reproduction (influenced by gamete production, fertilisation and carrying a pregnancy to term. In English language, the term was originally applied only to females, but increasingly is applied to males as well, as common understanding of reproductive mechanisms increases and the importance of the male role is better known. Infertility is a deficient fertility.