I assume that the expression is 4/5 (thanks to the rubbish browser, the division symbol is not visible). In that case, 5 is the denominator (or divisor).
The symbol 'π' is the Greek letter 'p' which is called "pi", like our 'p' is called 'pee'.
A power or exponent.
In an expression p4 is called a term.
The expression of a gene is called the phenotype.
algebraic expression
it is called a variable
Those are the "terms" of the expression.
A new invented word or expression is called a Neologism.
is one symbol already an expression in math
The a in circle symbol is the symbol for the word At. Example: soanso@(at)something.ca
& is called the ampersand.
The symbol representing the word "and" is called an ampersand (&).
I assume that the expression is 4/5 (thanks to the rubbish browser, the division symbol is not visible). In that case, 5 is the denominator (or divisor).
a variable expression in math is a symbol that is in a sentence
It means that the number or expression on the left of the symbol is less that the value or expression to the right, or that they are equal.
The real name of the symbol "&" is an ampersand. It is a logogram representing the word "and."