Yemen. The World Health Organization has reported over 900,000 cases and nearly 2200 deaths due to cholera from April to November 2017 in Yemen.

Chronic. High blood pressure, arthritis and high cholesterol are considered common chronic medical conditions.

Yogurt. Dairy products, such as yogurt and milk, are one of the best sources of calcium.

Synapses. A synapse allows a neuron to pass an electrical or chemical signal to another cell.

Hematocrit. The normal range of red blood cells is 41-50% for men and 36-44% for women.

Christine "George" Jorgensen. In 1952, George Jorgensen became Christine Jorgensen after the world's first sex-change operation in Denmark.