The Controlled Vocabulary service (which is similar to AutoComplete) expands user searches with words and phrases that constitute variations of the search term with the same meaning, thereby increasing the accuracy of the users' searches. The expansions are visible on the screen and add, for example, variations of the search term with the same meaning (example ADHD and attention deficit disorder).

Users are provided with an option to revert to using only their original search term. For example, if the user enters heart attack in the query, LocatorPlus Catalog also returns results that include myocardial infarction. If the user is interested only in results that include heart attack, the user can click the link to the right of the recommendation.