Definition:Order


 * Order of an Algebraic Structure.


 * Order of an Element in a Group.


 * Order of an Integer: the least positive integer $$c$$ such that $$a^c \equiv 1 \left({\bmod\, n}\right)$$.


 * Order of a Polynomial (otherwise known as its degree).


 * Order of a Derivative: the number of times a function has been differentiated.


 * Order of a Differential Equation: the highest order derivative that appears in that differential equation.


 * Ordering.