demography is the statistical study of populations and how they change over time. A demographic is a section of the population group based on some commonality. Now, age structure is the number of individuals of each age that are alive. You can see a generic representation of this here and an actual chart showing Libya's age structure in 2011. Now a generation is a term that refers to the average age between a mother's first offspring and her daughter's first offspring. Essentially, it's a way to kind of gauge, like the turnover rate, the rate at which your offspring can, on average, start having their own offspring. Now the life a life table is, ah, statistic group of statistical data for population that will relate to their life expectancy and death rate, or how long they're expected to live and through the rate at which members of the population are dying. Now, an age classes a group of individuals of a specific age, and here you can see a variety of age classes in this life table for the U. S. Population in 2003. Here are some of thes statistical measures you don't really need to worry about any of this, just giving you an example of what it might look like now. Often, researchers will use cohorts these air groups of individuals that share a characteristic and are usually studied over a period of time So the researcher will return to these individuals throughout time. Thio continue their study with that, let's go ahead and turn the page.