# What symbol?

1. Aug 21, 2010

### Shaybay92

My lecturer used a symbol in class that represents an element being removed from a set to form a new set. Does anyone know what this symbol is?

2. Aug 21, 2010

### HallsofIvy

There is no standard symbol for that specific operation but your instructor is free to define one. What symbol did he use?

3. Aug 21, 2010

### Shaybay92

Well that was the issue, I dont remember what the symbol was, I thought it was a standard.

4. Aug 21, 2010

### CRGreathouse

$$\setminus$$ or \ is probably the most common; - is sometimes used instead.

5. Aug 22, 2010

### HallsofIvy

The "\" crossing out a figure meaning it has been removed- erased if you like.

Often, you will see something like "^" directly over a symbol to mean it has been removed.

6. Aug 22, 2010

### CRGreathouse

Oh. I meant like $\{1,2,3,4,5\}\setminus\{2,3\}=\{1,4,5\}$.

7. Aug 22, 2010