What does the prefix ill mean?

The prefix "ill-" generally means not, lacking, or bad. It's often used to indicate a negative or undesirable state or quality.

Here are some examples:

* Illogical: Not logical

* Illiterate: Lacking the ability to read and write

* Ill-tempered: Having a bad temper

* Illness: A state of being unhealthy

* Ill-fated: Marked by bad luck or misfortune

The prefix "ill-" can sometimes have a more nuanced meaning, depending on the context of the word. For example, "ill at ease" implies a feeling of discomfort or anxiety, while "ill-advised" suggests something that is unwise or poorly thought out.