Spears and javelins. What is the difference between a javelin and a spear? A spear is a long stab weapon used both in hunting and in battle, whereas a javelin is more likely to be thrown. A spear is the basic infantry weapon, especially for those warriors who stood in the front line. The Roman javelin was called a pilum, and it had a particular shank construction that made it unique, whereas the Celtic spear had a similar shape to the spears used in the later medieval era.