| death rate | the number of deaths per 1000 individuals annually within a population |
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| delta | the often triangular-shaped alluvial deposition area at the mouth of a river |
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| demographic equation | the forumula that calculates population change. the increase (or decrease) in population is births minus deaths plus (or minus) net migration. |
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| demographic transition | a model that explains the long-term changes of brith and death rates in a society |
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| demography | the study of population statistics and trends, such as births, deaths, and disease |
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| density | the number of items per unit area, such as persons per square kilometer |
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| desert | an area with little precipitation or where evaporation exceeds precpitation, and thus includes sparse vegetation. |
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| diffusion | the spread of ideas, disease, technology, etc. among places |
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| doubling time | the amount of time for a given population to double, based on the annual growth rate. to determine doubling time, divide the growth rate as a percentage into 70. i.e., a growth rate of 3.5 represents a doubling time of 20 years |
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