Skip to Main Content

Web of Science: Using a Citation Database: Combine Search Terms: Practice

Search Operator Precedence

If you use different operators in your search on the  Web of Knowledge platform,  the search is processed according to this order of precedence:


Launch Web of Science

Web of Science can be accessed using the link below.  This link, along with the links to Web of Science on the library homepage and the databases page, allow users to access the resource from both on- and off-campus.

Search Operators

As in PubMed, you can usethe Boolean search operators AND, OR and NOT to combine terms. Web of Science also allows two more search operators: NEAR and SAME

  • Case is not important. OR, Or as well as or return the same results.
  • AND, OR and NOT can be typed into your search or selected from the drop down menus on the Search page.

AND finds records containing all terms. AND narrows your search.

  • Example: the search gene AND expression will find records where both the word gene and the word expressionappear.
  • Tip: AND is implied when you type in more than one word in your search. Example: the search gene expression returns the same search as gene AND expression. To get records where the exact phrase "gene expression" occurs, put your phrase in quotation marks.

OR finds records containing any of the terms. OR broadens your search. Use OR to combine synonyms and word variants. Example: HER2 OR ErbB-2 OR ErbB2.

NOT excludes any records containing the search terms from your results. NOT narrows your search — use it with care, because it can make your search too narrow. 

NEAR/n finds records containing all terms within a certain number of words (n) of each other. Example: cognitive NEAR/3 testing will find records where the words cognitive and testing appear within three words of each other. This search is much more precise than the search cognitive AND testing (or cognitive testing).

SAME can only be used when you are searching in an Address field. Use it find terms in the same line of the address.


Tip: Use SAME to find articles by Mount Sinai authors. An Address search for Mount Sinai SAME (New York OR NY OR 10029) will find articles by authors from Mount Sinai in New York. It will not find articles where one author is from Mount Sinai in Toronto and a co-author from New York University.

Compose your search with care.

Be Careful About the Order of Your Search Operators. Use Parentheses.  Web of Science processes search operators in a distinct order, so it's important that you use parenthesis to group terms correctly.  Web of Science assists you in this regard. If you are using multiple search boxes, Web of Science automatically puts parentheses around all the search terms you put in a single box.

Search order precedence comes up most often when you need to construct a search using both AND and OR.

AND takes precedence over OR, so Cancer AND HER2 OR ErbB-2 OR ErbB2 finds all records in which Cancer and HER2 are present as well as all records with either ErbB-2 or ErbB2. That is over 20,000 records. More to the point, these results are NOT correct. Records with ErbB-2 or ErbB2 may not include the term cancer.


> 43,000 records



To avoid search syntax errors, best practice is to put the terms you wish to combine with OR into one single search box or to enclose them with parentheses.

Example: Cancer AND (HER2 OR ErbB-2 OR ErbB2) finds records where cancer is present in a record with either HER2 or ErbB-2 or ErbB2. This search retrieves fewer results  — and results that are more on target.


> 37,000 records




> 37,000 records




Try It

Make sure you have removed any earlier date limits.

  • Search for miRNA AND dementia.
    You should retrieve about 39 citations. (Note that Web of Science did not map miRNA to microRNA, as PubMed would have.)

  • Now, search for miRNA OR microRNA and dementia.
    You should retrieve over 27,000 records: every record that mentions miRNA as well as all records that mention microRNA and dementia.

  • Finally, search for (miRNA OR microRNA) AND dementia.
    You should retrieve about 65 citations. This search is on target: it has more
     results than the first one because it retrieves titles like MicroRNA-29b Regulates the Expression Level of Human Progranulin, a Secreted Glycoprotein Implicated in Frontotemporal Dementia, not found in the first search. And, it does not have every record on miRNA in the Web of Science, only those which also pertain to dementia.