1. Variable symbol: usually expressed by letters, such as X, Y, Z, etc. These symbols represent independent or dependent variables of a function.

2. Function name symbols: usually expressed by letters, such as F, G, H, etc. These symbols represent the function itself and are used to indicate the definition or reference of the function.

3. Bracket symbol: Function expressions are usually identified by brackets, such as f(x), g(x, y), etc. Parentheses are used to enclose independent variables and play the role of grouping or parameter passing in function expressions.

4. Operation symbols: Function expressions can contain various mathematical operation symbols, such as addition symbols (+), subtraction symbols (-), multiplication symbols (*), division symbols (/), exponential symbols (or * *) and so on. These symbols are used to represent mathematical operations in functions.

5. Equal sign: Usually, the equal sign (=) is used to indicate the definition of a function or the equality relationship of an equation, such as f (x) = x 2, indicating that the definition of function F is the square of X. ..

6. Qualifying symbols: The common qualifying symbols in functions include summation symbol (σ), integral symbol (∩), derivative symbol (d/dx) and limit symbol (lim). These symbols are used to represent specific operations or mathematical concepts.

This is just a common example of symbols in functions, and the specific symbols used in mathematics and engineering fields may be different. Other symbols can also be used to represent functions and operations according to specific contexts and conventions.