An element is a weapon used by both HiMEs and Otomes
Element is the name for the objects the HiMEs can create. Most take the form of some kind of weapon, but a couple have non-combat functions such as Yukino's mirrors. All natural HiMEs wield Elements, while artificial HiMEs cannot.
The weapon of an Otome which she is able to materialize. Elements can take virtually any form and have multiple special powers. A rather puzzling fact is that a Meister GEM might have several versions of the element. For example, the element that Arika uses before she destroys her mother's body is different than the one she uses after.