Free text queries are performed by ESSENCE users very often. And increasingly, those free text queries are incorporating negation terms that allow the users to find case definitions when certain terms are not present. This video attempts to explain some of the special cases where negation in free text queries may be confusing for users. The video will mention some features in ESSENCE that you may not be familiar with like the Explain Query button and Advanced Query Tool (AQT). AQT is explained in the online training (https://www.surveillancerepository.org/essence-online-training-course) and training pdf (page 52: https://www.cdc.gov/nssp/documents/essence-training-presentation-phi-conference.pdf). The Explain Query button is a recently added feature found on the Query Portal that shows users more details about the queries they are about to run. Examples of use for this feature can be seen in the ESSENCE Q and A webinar here: https://www.surveillancerepository.org/essence-q-v20.