The terms "spear" and "pike" are often used interchangeably, and the distinction between them can vary based on historical context and usage. However, there are generally recognized differences between the two:

1. Length: A pike is typically longer than a spear. Pikes are known for their significant length, often measuring around 10 to 20 feet (3 to 6 meters) or even longer. They were used in formations of massed infantry or by polearm-wielding soldiers, relying on their reach to keep the enemy at a distance. In contrast, spears are generally shorter, typically ranging from around 5 to 9 feet (1.5 to 2.7 meters).
2. Design and Purpose: Pikes were primarily designed for thrusting attacks and were used in formations to create a wall of long weapons that could deter cavalry charges and break enemy formations. They usually had a long, narrow head with a sharp point, and their primary function was to keep the enemy at bay. Spears, on the other hand, can have various designs and purposes. They can be used for thrusting, throwing, or even as multipurpose tools.
3. Usage and Historical Period: The term "pike" is often associated with the late medieval and Renaissance periods, when long pikes became a dominant weapon on the battlefield. Spears, however, have been used throughout history in various cultures and time periods, ranging from ancient times to the present day.

It's important to note that these distinctions are not universally applicable, as there can be variations and overlap in terminology and usage across different historical periods and regions. The specific terminology and characteristics of spears and pikes can vary based on cultural, historical, and regional factors.