In many medical terms, what joins a root word to a suffix?

In many medical terms, a combining vowel joins a root word to a suffix.

A combining vowel (usually O or I and less frequently U) is used between two elements of a medical term to make the term easier to pronounce.  The other vowels may also be used, but less often.

Example:

explanation:

b the manazanar relocation center was located in california. it was used to keep japanise from spying on america.

the reasons for the harsh treatment, is because japan used tourist to take pictures and snapshots of pearl harbor.

many americans were afraid that the japanise would betray them for their mother country. through and means necessary. this means that, the leadership in japan is a lot different than it is here. culture and family ties has much to do with their outlook and worldview.

the answer is a (apex)