The following is from Turabian, 9th Edition, as is.
“15.2.1 Situations Requiring Citations
Chapter 7, particularly 7.9, discusses in depth when you should cite materials from other sources. Briefly, you should always provide a citation in the following situations:
-when you quote exact words from a source (see also chapter 25 on quotations)
-when you paraphrase ideas that are associated with a specific source, even if you don’t quote exact words from it
-when you use any ideas, data, or methods attributable to any source you consulted.
As noted in 15.1, you may also use citations to point readers to sources that are relevant to a particular portion of your argument but not quoted or paraphrased. Such citations demonstrate that you are familiar with these sources, even if they present claims at odds with your own.
From Section 7.9
You run that risk when you do any of the following:
▪  You quote, paraphrase, or summarize a source but fail to cite it.
▪  You use ideas or methods from a source but fail to cite it.
▪  You use the exact words of a source and you do cite it, but you fail to put those words in quotation marks or in a block quotation.
▪  You paraphrase a source and cite it, but paraphrase too closely (see 7.9.2).”
