Hypergamy (colloquially referred to as marrying up) is the act or practice of seeking a spouse of equal or higher socioeconomic status, or caste status than oneself.
The term is often used more specifically in reference to a perceived tendency amongst human cultures for females to seek or be encouraged to pursue male suitors that are comparatively older, wealthier or otherwise more privileged than themselves. Hypergamic behaviours can be explained in terms of genetic economic necessity, in which societies with high levels of gender inequality are more likely to have women who "marry-up" for the benefit of their children, and more likely to have men who "marry-down" to ensure that their mates have a higher incentive to remain faithful.
The word "hypogamy" typically refers to instances of the inverse occurring: marrying a person of lower social class or status.
Hypergamy: women only marry upward, never downward..even in 3rd world countries.