√2 means "the square root of 2." The symbol √ is a single character representation of the radical symbol that would normally have an over-bar extending over the radicand. When using the √ symbol, it is necessary to enclose the radicand in parentheses so there is no ambiguity as to meaning. Example √x+2 could mean √(x+2) or it could mean (√x)+2, for example.