The opposite of apple, but still denoted by the same name, could be a fictional fruit called "Nelppa." In terms of its characteristics, Nelppa would have contrasting qualities compared to an apple. While an apple is typically sweet, round, and red or green in color, Nelppa could be sour, square-shaped, and blue or yellow in color. This would create an opposite yet parallel concept between the two fruits, representing the collision equation of +1 and -1 resulting in 0.