# What does Δx mean?

1. Sep 26, 2011

### MarcAlexander

So I'm aware that the triangle is uppercase delta which means the difference between: 10$\Delta$5=5

But what does Δx mean?

2. Sep 26, 2011

### DrGreg

It means the difference between two values of the variable x, between two specified events.

3. Sep 26, 2011

### noxxo

It means the change in x. For x(at event 1) = 2 and x(at event 2) = 4 : delta x = 4-2 = 2

4. Sep 26, 2011

### nonequilibrium

sometimes it is also used to refer to uncertainty in the variable x
what kind of "uncertainty" depends on the context: experimental, or pertaining to it being defined, ...

5. Sep 26, 2011

### brocks

Actually I've never seen that use of it. I'm not saying it's wrong, but it's unusual.

But in elementary math texts, $\Delta$x means the amount of change in the variable x. For example, the slope of a line is $\Delta$y/$\Delta$x, i.e. the change in y divided by the change in x, for any two points on the line.

When you learn calculus, you will see that the instantaneous velocity of an object travelling along the x-axis is the limit of the displacement divided by the elapsed time, $\Delta$x/$\Delta$t, as $\Delta$t approaches zero.

6. Sep 26, 2011

### Allenman

$\Delta$x = x$_{2}$-x$_{1}$

or the slope of a function:
$\frac{\Delta y}{\Delta x}$ = $\frac{y_{2} -y_{1}}{x_{2}-x_{1}}$

Which you'll find to be very similar to the definition of a derivative in calculus:
$\frac{\delta y}{\delta x}$ which basically means (difference in y)/(difference in x)

Capital delta is looking for a specific answer (most times) while lower case is looking for another equation (most times).

Last edited: Sep 26, 2011
7. Sep 27, 2011

### MarcAlexander

What book would provide me with a quick reference to the use of greek letters in Physics?

8. Sep 27, 2011

### Pythagorean

Most symbols have different meanings in different contexts. Pi is one of the few symbols that has a consistent meaning.

9. Sep 27, 2011