Required (+)
Selecting this operator means that the term must appear somewhere in the formulation result.
Using the Required operator with two or more terms acts as the Boolean "and"; for example, the below query equates to "Rilpivirine" AND "Dolutegravir":
After submitting the query, the Required operator converts to a "+" sign in the search bar and search history.
Excluded (-)
Selecting this operator means that the term must not appear in the formulation result.
Using the Excluded operator acts as the Boolean "not"; for example, the below query equates to "Rilpivirine" NOT "Dolutegravir":
After submitting the query, the Excluded operator converts to a "-" sign in the search bar and search history.
Optional
Selecting this operator means that the term does not have to appear in the formulation result to be considered a match.