Would this be considered a case of plagiarism? I finished writing a report for a course (in my undergrad) and I submitted it to Turnitin for a similarity check (8%) and in one part I noticed it highlighted fragments of one sentence.
The flagged sentence has about 8 words in a row in a 26-word sentence that matches another report but the sentence itself is different than the one Turnitin says it is similar to.
I did paraphrase this sentence from a completely different source with appropriate in-text citation and bibliography and ensured I wasn't using any direct quotes from that source. That being said, I am concerned that because the technical wording is so similar to what Turnitin picked up (those 8 words in a row that are the same) it might be cause for concern.
Sorry, I don't know if I'm being paranoid or if I should legitimately be worried.
For coursework, some professors have a stricter definition of plagiarism than is strictly necessary. But, from what you say, you have cited the original and if it is clear enough that your citation implies that the source of the ideas is elsewhere, then it isn't technically plagiarism.
Note that whether you quote or paraphrase is irrelevant, assuming you quote properly (quote marks or a set aside of some sort). Plagiarism is about the idea itself, rather than the specific words.
Automatic plagiarism checkers do a poor job, actually, giving both false positives and false negatives. But if you cite (what the checker said overlapped) properly, it isn't plagiarism.
Another issue, frequently forgotten, is that for some sorts of things, especially in, say, math, there is effectively only one way to say something and some things are also common knowledge. So, for these things, neither plagiarism nor copyright actually apply. This probably doesn't apply in this specific case, but keep it in mind, generally.