The number of deaths occurring in a population during a given period of time, usually a year, as a proportion of the number in the population. Usually the mortality rate includes deaths from all causes and is expressed as deaths per 1000. A disease-specific (or age-specific or sex-specific) mortality rate includes only deaths associated with one disease (or age or sex) and is reported as deaths per 1000 people of the specified type. The mortality rate may be standardized when comparing mortality rates over time, or between countries, to take account of differences in the population. See also age-specific rate; sex-specific rate.