Repetition is a rhetorical device meant to make ideas more memorable, as well as to create structure and to emphasise important points.
The most significant example in this TED talk is Adichie's use of anaphora in series of rhetorical question: “What if my roommate knew about the heart procedure that was performed in the Lagos hospital last week? What if my roommate knew about contemporary Nigerian music (…) What if my roommate knew about Nollywood (…)”. This repetition is meant to draw attention towards all the aspects of African culture and diversity that are usually ignored or unknown by Westerners.
Another example is Adichie’s repeated use of the word “stories”. This is especially evident at the end of the speech:
“Stories matter. Many stories matter. Stories have been used to dispossess and to malign, but stories can also be used to empower and to humanize. Stories can break the dignity of a people, but stories can also repair that broken dignity”.
This repetition is meant to emphas...