Hello and welcome to Android Forums. Hopefully I can help you with your problem.
It depends on which Android phone you have. Some will allow you to mute it with a verbal command or a wave of your hand over the device while others require you to press a button.
There are many 3rd party alarm apps available on Google Play that offer features the stock alarm doesn't.
As for your stock alarm, read through the alarm settings completely. If it has an option to mute the alarm, that's where you'll find it.
If you have any other questions regarding your device, I invite you to join Android Forums. We have many sections for specific devices which contain a wealth of information.