# Understanding the e:, evt: etc in a function

**URL:** <https://forum.kirupa.com/t/understanding-the-e-evt-etc-in-a-function/307138>\
**Category:** flash\
**Created:** [March 29, 2010, 12:39pm UTC](https://forum.kirupa.com/t/understanding-the-e-evt-etc-in-a-function/307138 "2010-03-29T12:39:09Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![fs\_tigre](https://avatars.discourse-cdn.com/v4/letter/f/edb3f5/32.png) [@fs\_tigre](https://forum.kirupa.com/u/fs_tigre)\
**Post date:** [March 29, 2010, 12:39pm UTC](https://forum.kirupa.com/t/understanding-the-e-evt-etc-in-a-function/307138/1 "2010-03-29T12:39:09Z")

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Hi,

I have been using functions since the first day I started using Actionscript 3.0 in fact I think is one of the first things I learned but I guess I never had a good understanding as to why the use of the “evt:” I know this is probably something I should already know but as you can see I don’t (shame on me).

Can someone explain me what is the purpose of the evt: , e: and event:(I guess this can be anything)?

```auto
addEventListener(MouseEvent.CLICK, someFunction);
  function someFunction(e:MouseEvent):void{}

```

I understand the need of MouseEvent since we need to tell the function the type of event we are looking for but what is the “e” doing?

Is “e:” some sort of local variable that never gets referenced?

Can someone be so kind and give me a brief explanation, I want to have a better understanding and not just do it without having any idea why?

Thanks