Using other peoples' code to learn something new. I do it all the time, for instance right now while building my website. The JavaScript in it has been retrieved from various places on the Web, and edited (using a plain text editor) to fit the situation at hand. This kind of CodeReuse is faster and easier than creating it all from scratch.

''A concept we all know so well. It has to have been mentioned somewhere before on Wiki. I've always called this CopyAndPasteReuse. It's the most common and surely often the most useful kind. Industry-wide, it's why OnceAndOnlyOnce has an ever-increasing mountain to climb.''