If you are hungover, you feel ill because you drank too much alcohol the evening before. Your head hurts, your mouth is dry, your stomach feels wrong, and light or noise can seem too sharp. You are not still drunk: the drink has mostly left you, but your body is paying for last night. Friends say it the morning after a party or a wedding. It is informal — natural in chat, a little loose in a formal letter. People also write it as two words, hung over. Though actually, people stretch it. You will hear “I feel hungover” after a very late night with no drink, or after too much sugar. That is playful. The real centre of the word is still last night’s drinking. The matching noun is hangover: that is the thing you have. Hungover is how you feel.