Sudanese means 'from Sudan' or 'having to do with Sudan'. It works two ways. As an adjective: Sudanese food, the Sudanese government, a Sudanese passport. As a noun it means a person from Sudan: 'She is a Sudanese', though most speakers prefer 'She is Sudanese' with no 'a', which sounds more natural and less like you are labelling someone. The important grammar point is the plural: it does not change. One Sudanese, two Sudanese, many Sudanese — never 'Sudaneses'. And 'the Sudanese' means the people of Sudan as a whole group. This is the same pattern as Chinese, Japanese, Taiwanese, Portuguese and Vietnamese, all with the -ese ending. Since 2011 there has been a small problem of meaning: does Sudanese include people from South Sudan? Usually no. People from South Sudan are called South Sudanese. But older writing, and people who left before the split, may use Sudanese for both, so read carefully.