Indeterminate form
A limit expression like \frac{0}{0} or \frac{\infty}{\infty} whose value isn't determined by the form alone.
An indeterminate form is a limit expression — \frac00, \frac{\infty}{\infty}, 0\cdot\infty, \infty-\infty, 1^\infty, 0^0, or \infty^0 — that does NOT determine the limit's actual value just from its shape. The same indeterminate form can correspond to limits equal to 0, to a finite nonzero number, to \pm\infty, or to no limit at all, depending on the specific functions involved — the form only signals that more work (like L'Hopital's Rule or algebraic manipulation) is needed.
Examples
\lim_{x\to0}\frac{\sin x}{x} has the indeterminate form \frac00 but equals 1.
\lim_{x\to0}\frac{x^2}{x} also has the form \frac00 but equals 0 — same form, different value.
See also