Is copying a sentence considered plagiarism? In writing a phd thesis, if a sentence is copied as it is and given proper references, then will it be considered as plagiarism?
Verbatim cited text is preferably put between quotation marks. E.g., Smith et al. (Smith 2008) state: "literally copied text goes here."

If you use quotation marks to indicate the verbatim copied text, it is not considered plagiarism.