What are adverse events, adverse effects, side effects, and adverse drug reactions?

If we look at the official, FDA-approved Prescribing Information for any medication, we see a few different terms being used for the undesirable effects of the medication. For example, in the Prescribing Information for esketamine nasal spray (Spravato®), we see the following ( highlights added by us): What is the difference between these terms? Adverse…