Whenever I have been designing interfaces, I always wonder if I should name the button Create, New or Add. I have never decided and stuck with one and would like to get an explanation on what use cases apply to each?

To me it seems that Add would indicate some sort of real life object / data is just being added to the application such as a location. Whereas New would imply a brand new piece of data, an example being a new user group or category.

Create I am not sure on, hence a nice clarification would be appreciated and if I was even remotely close to the actual and perceived meanings in design.

Or should I just stick to one of the keywords throughout the whole application? As to not confuse users.