Mononucleosis is an illness, the one people usually call mono. You feel washed out, your throat hurts, and the glands in your neck swell. A virus causes it, and it moves in saliva — the wetness in the mouth — which is why people joke that it is the kissing disease. Teenagers and young adults get it more than little children. It is not usually dangerous, but getting your strength back can take weeks. Doctors named it for what they see in the blood: more of a certain white cell that has one nucleus. Though actually, in everyday talk almost nobody says the long word. They say mono, and they mean this illness, not the little prefix that means “one” on words like monolingual.

傳染性單核球增多症（口語常叫「接吻病」；中國大陸書面較常用「單核細胞增多症」）