Historically speaking there seems to be some confusion as to whether a morning star is a flail, defined as "a medieval weapon made of one (or more) weights attached to a handle with a hinge or chain." or a mace, defined as "a strong, heavy wooden, metal-reinforced, or metal shaft, with a head made of stone, copper, bronze, iron or steel". Now, usually we consider a morning star to be combination of a mace and a flail. The weapon is constructed of at least one spiked ball which is attached to a haft by a metal chain. However, there may be more than one spiked ball and chain utilized which is what often causes the problems in defining the weapon accurately.
Some examples of the help on research paper about morning star show them being pole arms – over 6 feet long. Others have them as side arms, to be wielded by one hand while the other hand employed the use of a shield. Again, the problem with the name. Oddly enough morning stars have other names as well, being called "holy water sprinklers" due to the fact that they somewhat resemble the aspergillum used by the church to sprinkle parishioners with holy water, and "goedendag" or "good day".
In modern times the term morning star is mostly used in fantasy role playing games, which is where one would most likely encounter the weapon outside of a museum or weapon shop. In the games, a morning star is a flail, or at the least a combination of a mace and flail. Also, this weapon is used by the priests and clerics more than by any warrior class in a role playing game. These classes are usually restricted to using bludgeoning weapons, such as a mace, warhammer, or quarterstaff. Odd isn't it that a weapon removed from tournaments due to its lethal damage to be classified with those weapons that bludgeon rather than pierce.
It would seem that there is no strict definition of which weapon the morning star actually is and that it would fall to the owner of the weapon as to which he prefers. Is it a mace? Yes. Is it a flail? Yes. What is it best known as? Maybe the holy water sprinkler, or maybe just the morning star.