It's the source of many English words, including:
* Malady: A disease or illness
* Malice: The desire to harm someone
* Malicious: Characterized by malice or spite
* Malcontent: A person who is dissatisfied with the existing state of affairs
* Malfunction: A failure to work correctly
* Malpractice: Negligent or improper conduct by a professional person
* Malevolent: Having or showing a wish to do evil to others
* Malnutrition: A lack of proper nutrition
* Maladjusted: Not well adjusted to one's environment or society
So, whenever you see "mal" in a word, it's a good indicator that something bad or negative is involved.