This is a rather cool quick tip that can save you a lot of time. Most modern search boxes now a days have a drop down auto-complete feature to help you complete words a lot quicker, this is generally useful and can save you some time and effort. Wouldnt it be useful if you could expand this auto-complete feature to more text boxes around your operating system. Thankfully you can. Simply press Command + Period (or full stop) and your Mac will bring up a list of words which you can use to complete the word you are typing.
This drop down menu appears in pretty much any text box areas such as Mail, TextEdit to name a few. You start typing a word, press Command + Period and a list will appear that you can scroll through and use to complete the word you are typing. Useful if you have a long word that have a very specific start and you dont want to type the whole thing out. You can scroll through with the arrow keys and select your work with either the tab or return/enter key.
Unfortunately this auto-complete doesnt quite work like the one on Googles search box. If you bring up the menu and then start typing the menu will disappear, hopefully this feature will be improved in new versions of the OS. Having said that, words you auto-complete frequently will appear at the top of the list as well as words already in the document or text box you are using, allowing you to save those few partial seconds. Its seems this feature will only work with certain textbox area and fields so try it out in different text areas and see what happens.
An intereting feature that I just found out and thought you might be interested in. If you want to learn more this is the sort of trick that appears in Mac OS X Snow Leopard: The Missing Manual.
Edit: It seems in a previous post I have already covered this topic, however that was using the keys Option + Esc or F5. It seems there are many key commands to complete the same task.
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