Here's why:
* Prefixes add information: Prefixes are word parts added to the beginning of a word. They usually modify the meaning of the root word in a specific way.
* "Bi" and "Tri" indicate quantity: "Bi" means two, and "tri" means three. So, adding these prefixes indicates a doubling or tripling of the concept expressed by the root word.
Examples:
* Bicycle: "Bi" (two) + "cycle" (wheel) - a vehicle with two wheels.
* Triangle: "Tri" (three) + "angle" (corner) - a shape with three angles.
* Bilingual: "Bi" (two) + "lingual" (language) - able to speak two languages.
Therefore, adding prefixes like "bi" or "tri" creates new words with different meanings, often related to quantity or number.