In algebra, a nested radical is a radical expression (one containing a square root sign, cube root sign, etc.) that contains (nests) another radical expression. Examples include
5 − 2 5 , {\displaystyle {\sqrt {5-2{\sqrt {5}}\ }},}
which arises in discussing the regular pentagon, and more complicated ones such as
2 + 3 + 4 3 3 . {\displaystyle {\sqrt[{3}]{2+{\sqrt {3}}+{\sqrt[{3}]{4}}\ }}.}