Here are some examples of words that use the root "mal":
* malady: a disease or ailment
* maladjusted: poorly adjusted or adapted
* malfunction: to fail to function properly
* malicious: intending to do harm
* malpractice: improper or negligent professional conduct
* malnourished: lacking proper nutrition
* maltreat: to treat badly or cruelly
The prefix "mal-" is often used to create words that have a negative connotation.