The evil eye is a look that is believed by many cultures to be able to cause injury or bad luck for the person at whom it is directed for reasons of envy

Envy

Envy is best defined as a resentful emotion that "occurs when a person lacks another's superior quality, achievement, or possession and either desires it or wishes that the other lacked it."...

 or dislike. The term also refers to the power attributed to certain persons of inflicting injury or bad luck by such an envious or ill-wishing look.

The "evil eye" is also known as ''ʿayn al-ḥasūd (عين الحسود) and mal de ojo.

The idea expressed by the term causes many cultures to pursue protective measures against it.