Combining words
Correlation between search terms
If you are using several search terms at the same time, you need to indicate what exactly the correlation between these terms is. There are three basic types of correlation between search terms:
- Both terms need to occur in the search result (AND), for example football AND Amsterdam.
- At least one of the terms needs to occur (OR), for example football OR tennis.
This can also be useful when using synonyms, for example senior citizens OR elderly people. - One term needs to be excluded (NOT), for example sport NOT football.
These types of correlation between search terms can be represented by the following diagrams:
Sometimes, you will have to specify the correlation between search terms yourself by typing AND, OR and NOT.
In most databases and search engines, you will find a search form under advanced searches from which you can choose one of these options. Often it is also possible to combine the various options.
Example
You are searching for information on the correlation between the greenhouse effect and coal-fired power stations. You wish to find publications containing both terms.
You suddenly realise that global warming is an important alternative term for greenhouse effect. You modify your search in such a way that the term coal-fired power stations occurs in combination with either one of the terms greenhouse effect or global warming. .
N.B. If you are combining search terms using both AND and OR, you will need to use the OR combination within one search field (see above picture) in most advanced search forms. Should you omit this, the database will not know which search terms to combine first, leading to undesired search results.
At this stage, you are not interested in the political aspect of this matter. You are searching for articles about coal-fired power stations using this term in combination with the terms greenhouse effect or global warming, but without the term politics.
In many databases and some search engines, you can also carry out complex searches by nesting. See also Nice to know: Nesting terms.
