Alias won't save in terminal

I am having a go using the terminal on my mac, when I set up a alias it works fine while the window is open but does not save it, so when I re-open the terminal my alias is not working. Any ideas?

You need to create the alias in a script file which is executed each time you log in or start the terminal. I’m not a Mac user, but on other *nix systems the file is normally named .login or .bashrc or similar. List your dot-files (ls -a) and you’ll probably find which one to use.

Thanks for pointing me in the right direction