yeast infection (Also called Candida.) - one type of vaginitis caused by the Candida fungus characterized by itching, burning, or redness of the vaginal area.
yellow fever - a viral disease that is transmitted by the Aedes aegypti mosquito.
Yin and Yang - Chinese words for complementary and opposite forces that make up the life force (Qi).
yoga - Indian word for "union." Yoga is a posturing and breathing technique to induce relaxation.