One possible theme of "A Raisin in the Sun" is that people often become frustrated after experiencing injustice.
The story follows the Youngers, an African-American family, in 1950s Chicago. Mr. Younger had died and the family is awaiting a $10,000 inheritance. The family members have different ideas of how to better their financial situation with the money, but the decision was ultimately made by Mama. Mama puts some of the money down on a house and decided to give the rest to Walter to invest in a liquor store as long as he promised to help Beneatha pay for her education to become a doctor.
The problem is that Walter gives the money to his acquaintances, who spend it all. The family becomes upset about the loss of money, so when the neighborhood where Mama bought the house, which happens to be an all white neighborhood, offers money to avoid racial conflict, the family considers it. However, Mama says they cannot accept it essentially because it would solidify the belief that people that are white are better than people that are black. Through these events the family experiences injustice and becomes frustrated with their lack of money and the racism in their society.