Side effect: A side effect is an effect of a drug, chemical, or other medicine that is in addition to its intended effect.
Therapeutic effect/ Adverse effect: An adverse effect is a harmful, undesirable effect that that result from a medication or other intervention.
Effects:
1- Side Effects can be both therapeutic and harmful.
2-Adverse Effects are generally harmful and undesirable.
Prior knowledge:
1-Side Effects are usually expected by the doctor.
2-Adverse Effects are not expected by the doctor.
Effect on the treatment:
1-Side Effects generally do not hinder the main effect of the drug.
2-Adverse Effects can hinder the treatment and lead to more complications.
Severity:
1-Side Effects are mild and self-resolving when compared to adverse effects.
2-Adverse Effects are more severe and life threatening.