Shift + Command + Colon: displays the spelling window.Control + Command + D: Shows the definition of a chosen word.Command + U: underline the chosen text or activate / deactivate the function.Command + I: Italicize the selected text or enable / disable the function.Command + B: Bold the selected piece of text or enable / disable the option.They allow you to move freely through a text you are writing at the moment as well as being able to edit it easily. If you work a lot with documents, either in word processors such as Word or Pages, or in the Preview application, these shortcuts interest you. Option + Command + Escape: force quit an application.
Command + C : copy action to clipboard.