Is there a difference between the minus sign in a negative number and the unary minus operator which is essentially a function over a particular set mapping a number to it's negative?
For example $-7$ is a number and is the negative sign indicate the unary minus function -(7) or just part of the numeral? The confusion is due to the fact that $-x$ seems to indicate the unary minus function but also looks as if it is written in the same way as $-7$
Unary Minus Sign
algebra-precalculusnotation
Best Answer
The unary minus symbol $-$ denotes the function from $\mathbb R$ to $\mathbb R$ such that $-x$ equals the unique number $y$ satisfying $x+y=0$.
The symbol $-7$, by definition, means the result of applying the function $-$ to the real number $7$. And $-7$ is of course also a real number. This is in the same way that $\sin(5)$ is a real number that means the result of applying the function $\sin$ to the number $5$.
Even though $-$ is a function just like $\sin$ is, in practice we use different notational conventions for these functions. It would be strange to write something like $-^2(7)$.