Hàm số y = f(x) có giới hạn L khi x → x 0 có kí hiệu là:

\[\mathop {\lim }\limits_{{\rm{x}} \to {{\rm{x}}_0}} {\rm{f}}\left( {\rm{x}} \right){\rm{ = L}}\]

\[\mathop {\lim }\limits_{{\rm{x}} \to \infty } {\rm{f}}\left( {\rm{x}} \right){\rm{ = L}}\]

\[\mathop {\lim }\limits_{{\rm{x}} \to \pm \infty } {\rm{f}}\left( {\rm{x}} \right){\rm{ = L}}\]

\[\mathop {\lim }\limits_{{\rm{x}} \to {\rm{L}}} {\rm{f}}\left( {\rm{x}} \right){\rm{ = }}{{\rm{x}}_0}\]