Truncation is like a wildcard. Added to the stem of a word, it will find that stem plus anything that comes after it. The symbol used to truncate a word depends upon the database or Web search engine you are using.

psychol? will return records on psychology, psychological, psychologist.
? is used as the truncation symbol, for example, in CINAHL.
comput* will return records on computer, computate, computing.
* is used as the truncation symbol in Business Source Premier.