The javelin spear and short spear differ mainly in purpose, design, and combat use. A javelin spear is lightweight and balanced for throwing, making it ideal for long-range attacks. A short spear is heavier, built for thrusting in close combat, and offers better control and defense. Javelins prioritize distance and speed, while short spears focus on durability and hand-to-hand effectiveness, making each suited to different battlefield roles and fighting styles.