Answer:
The blacks in America were deemed inferior and only seen as someone lesser, like a young boy among adults. Maybe, this is one reason why Wright uses the word "boy" in his title.
Explanation:
Richard Wright's memoir "Black Boy" presents the author's childhood and also growing up years as a black man in the American South. The book deals with themes of growing up, racism, family, and also a sense of trying to find his identity.
The use of the word "boy" in the title is ironic because Wright may be describing his childhood experiences but at the same time, the memoir covers well beyond his childhood years too. This may also have to do with his feeling of still being a kid despite being an adult.
Also important is how the blacks were perceived by the whites, the "superior" whites. Though same in all senses, blacks were hardly accepted by the whites as their own or equals, and more like inferior and lesser than them. This can also be one reason why Wright uses the word "boy", as a generalization of how his black people were perceived by the whites.
