(2) Operation symbols: such as plus sign (+), minus sign (-), multiplication sign (× or), division sign (÷ or/), union of two sets (∩), intersection (∩), root sign (√), logarithm (log, lg, ln.
(3) relational symbols: such as "=" is an equal sign, "≈" is an approximate sign, "≦" is an unequal sign and ">" is a greater than sign. "
(4) Combination symbols: such as "()" in brackets "[]" and "-"in braces "{}".
(5) Natural symbols: such as positive sign "+",negative sign "-"and absolute value symbol "∨"
(6) Elliptic symbols: such as triangle (△), sine (sin), cosine (cos), function of x (f(x)), limit (lim), ∫ because, (one foot can't stand) ∴ so, (two feet can stand) and. ) and so on.
(7) Other symbols: α, β, γ and other symbols.