Writing & plagiarism

So you have to write stuff, like a thesis. There is just one iron rule of writing:

no plagiarism

How about copying something and changing some of the words?

NO!!!

How about writing something original in bad English?

Much, much less bad than plagiarism!

It's ok to copy, if the copied parts and the source are completely clear. Here's an example (from "The Data Loom" by Stephen Few). If you do something like this, be careful that it's sufficiently clear what parts are copied and where from: if in doubt, ask!