Every story has more than one side and by only acknowledging one we limit not only ourselves but our understanding of that story. Adichie also touches upon the fact that you cannot discuss stories without discussing power. Stories are directly correlated with power in the sense that a story is affected by who tells it and how it's told. This power allows that story to be the only way that it is told causing that single story to become definitive. Single stories can prove to be dangerous because they create stereotypes, emphasize differences instead of similarities and reduces balance.
Intersectionality: Intersectionality is a concept that helps to understand how different aspects of an individuals identity such as race, sex, sexual orientation has an effect on their place in the world and possibly how others understand their "stories". For example it is said that women have gained more power in the professional world and have taken greater steps towards equality among men. However this is usually the case mostly for white women. Women of colour such as black and Latina women have a harder time in the professional field as opposed to a white woman because not only are they women but they also have another aspect to their identity that affects their outcomes. Not only are they female but they are also of colour.