Disclaimer 1: I am not a lawyer, but I've done enough writing that I've had to research copyright law. Disclaimer 2: My research has been of U.S. law, and not Canadian. The legal systems of the two countries are similar, and copyright is mostly governed by international treaties so they should be similar, but I cannot assure you that they're the same here. That said:
Copyright protects the exact words or pictures used, not ideas. U.S. courts have repeatedly ruled that if you take something written by someone else, and then re-write it in your own words, you are not violating their copyright. I don't have the court citations but there was a big case many years ago where a news organization was taking another news organizations stories and rewriting them. The court ruled this did not violate copyright: You can't copyright a fact, only the words you use to discuss that fact. Like if the New York Times was the first to report that Senator Jones had won re-election, they could not then sue every other newspaper that also reported that Senator Jones had won, not unless that other newspaper copied the New York Times story word-for-word. (Or copied parts of it.)
You have a limited right to quote from what another person has said or written. This is called "fair use". There is no hard and fast rule here. Like there's no law that says you can quote 50 words but not 51 words. The legal principle is, Are you quoting enough of another person's work that someone might buy your book (or article or whatever) rather than the original? The law also gives more leeway if you are quoting someone for purposes of "education" or "literary criticism" than for commercial purposes.
Bear in mind that copyright is all about PROPERTY rights: you can't steal my work in a way that costs me money. It has nothing to do with originality of ideas or intellectual honesty. If you claim that some idea is original to you but you really got it from someone else, that may violate the academic principle of plagiarism. But plagiarism is not a crime: it's an academic violation. You can be kicked out of school or black-balled from academic publications for plagiarism, but you can't be sued or jailed. Anyway, you can pretty much 100% prevent accusations of plagiarism by giving proper credit. Giving credit does zero for charges of copyright violation. If you copied somebody else's entire book word for word, and then added a line that said, "This book is a copy of ...", that wouldn't help you in court at all. It would just be a confession of the crime.