The verbs derived from habere usually have an 'i' in the stem rather than an 'a'. For example, adhibere, exhibere, inhibere, and prohibere, leading to the modern English verbs adhibit, exhibit, inhibit, and prohibit.
Why did the stem vowel change when prefixes were added to habere to form new verbs?
This is mostly a matter of curiosity for me, since this seemingly arbitrary change, which nevertheless occurs in all of the verbs derived from habere by adding prefixes, except for antehabere and posthabere for some reason, makes the etymology of words like exhibition or inhibition more difficult to deduce (since there is no Latin word hibitio).