What is the exact name of the signs +, -, : and x?

Answer

Hi Jurgen

The symbols +, -, :, x indicate the 4 main operations.

The most general term for an operation is the operator.
The things the operator is applied to are called the operands.

Let’s apply this to a summation

2 + 3

+ : the operator (in this case the addition operation)
2, 3 : the operands (in this case the terms of the addition).

I hope your question has been answered here.

Kind regards,