Frequently asked questions 2 – Truncation

Questions about truncating search terms when searching databases:

  • Why is it necessary to truncate search terms?
  • How should I truncate my term?
  • What truncation mark should be used?

You do not always have to truncate your search terms but…

  • robots (search engines) only search for character strings, not for meanings
  • most terms have singular and plural forms, and also genetives


  • truncated patient* retrieves all these: patient, patients, patient’s
  • not truncated patient retrieves only patient
  • truncated child* retrieves child, children, child’s children’s
  • not truncated child retrieves only child

Different databases use different truncation marks. The most common are asterisk * and question mark ?. Check the database’s manual/FAQ if * does not seem to work. In PubMed, Cochrane Library and Scopus truncate using *. In Josku truncate using ?.

truncation marks

There are also irregular plurals so that the singular and plural forms are different in a way that truncation does not work.

For example:

  • foot/feet
  • mouse/mice
  • tooth/teeth
  • woman/women

In some databases it is possible to use so called wild cards and search for e.g. wom*n, but in many databases you have to search singular and plural combined with OR.

For example:

  • foot OR feet
  • mouse OR mice
  • tooth OR teeth
  • woman OR women

There are also irregular plurals that can be search by truncating.

For example:

  • criteri* retrieves singular criterion and pluralcriteria
  • nucle* retrieves singular nucleus and plural nuclei (and also nuclear, nucleic, nucleoid, nucleon…)
  • analys* retrieves singular analysis and plural analyses (and also analysand and analyst)
  • phenomen* retrieves singular phenomenon and plural phenomena (and also e.g. phenomenology)

Watch a video in YouTube about truncation.

By: Tuulevi Ovaska, Head of Services, Kuopio University Hospital Medical Library, University of Eastern Finland Library