Hot key for opening a file?

In windows, opening a file can be done by just pressing the Enter/Return key. But in Mac, pressing Return goes to renaming the file. Is there any other option to open a file using the keyboard, but an alternative to command+O?

I always hit the Return key because it has become a habit (switched to Mac from Windows XP), and the result is really annoying!

Replies will be great.
Thanks!

There's also Command + down arrow.

Thank you 'miles01110'.
So can I assume that a file/folder cannot be opened in a Mac with just one key?

Don't think so. At least I've never come across a single key that opens an app.