Tannin (noun)

1. A bitter-tasting organic substance present in tea, coffee, and other plants, which can be used to tan leather and as an astringent in medicine.
2. A bitter-tasting compound that is found in many plants, including tea, coffee, and wine, and is used to tan leather and as an astringent in medicine.

Origin:

From french tanin, from tan "tanbark".

Examples:

1. The tannin in the tea stained the cup.
2. The tannin in the wine made it taste bitter.
3. Tannin is used to tan leather.
4. Tannin is an astringent used in medicine.
5. Tannin is used as a food additive to preserve the color of the food.