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ghost – n. a very small amount or trace (as in ghost town, a town with few remaining inhabitants)
migration – n. movement from one area to another
mission – n. an important job or duty
sanction – n. a threatened punishment for disobeying a law or rule
tend – v. used to describe what often happens or what someone often does or is likely to do — followed by to + verb
motivated – adj. describes someone who has a strong reason for doing something
drain – n. a thing that uses up something; the continued loss of something
challenge – n. a call to take part in a competition
demography – n. the study of changes (such as the number of births, deaths, marriages, and sicknesses) that take place over a period of time in human populations also : a set of such changes
