Final answer:
The most common functional ovarian cyst is follicular cyst.
Step-by-step explanation:
The most common functional ovarian cyst is follicular cyst. An ovarian cyst is a sac filled with fluid or other material that develops in or on the ovaries. Follicular cysts occur when a follicle in the ovary does not properly release an egg and instead becomes a fluid-filled sac. They are usually harmless and often resolve on their own without treatment.