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Google Scholar interprets spaces as the AND Boolean operator (tip originated from Wichor Bramer). Example: Searching cancer AND treatment is equivalent to searching cancer treatment.
Google Scholar interprets the | symbol as the OR Boolean operator (tip originated from Wichor Bramer). Example: Searching cancer OR "malignant neoplasm" is equivalent to searching cancer|"malignant neoplasm" (note that there are no spaces around the | symbol).
Google Scholar interprets the dash as the NOT Boolean operator. Example: Searching for cancer NOT lung is equivalent to searching cancer -lung.
Please Note: The NOT operator should be used with caution, you may miss out on relevant results that discuss your topic and the topic you are 'NOTting' out of the search. More information on using NOT with caution.
Bramer, W. M., Giustini, D., Kramer, B. M., & Anderson, P. (2013). The comparative recall of Google Scholar versus PubMed in identical searches for biomedical systematic reviews: A review of searches used in systematic reviews. Systematic Reviews, 2(1), 115. https://doi.org/10.1186/2046-4053-2-115