Generation

A generation means any group that is sorted by the time they were born.

In a family, a generation means all the people on one level of a family tree.  For example, your brothers, sisters and cousins are in the same generation as you.

In populations of people, a “generation” means groups of people born in different periods of time. Each generation lasts for the average amount of time between the birth of parents, and the birth of their children.

Examples of generations:
Generation Beta: 2025 to 2039
Generation Alpha: 2013 to 2028
Generation Z: 1997 to 2012
Millennials: 1981 to 1996
Generation X: 1965 to 1980
Baby boomer: 1946 to 1964
Silent Generation: 1928 to 1945
Greatest Generation: 1901 to 1927
Lost Generation: 1883 to 1900

 Generational theory 
The sociologist Karl Mannheim (d. 1947) wrote about a theory of generations in his 1923 essay The Problem of Generations. 

One of the ideas, is  the "romantic-historical". In periods of rapid social change a generation would be much more likely to develop a cohesive character. Mannheim identified three (things in common, or) commonalities that a generation shares:

References

Category:Family
Category:Time