Kefir is a fermented milk drink that is similar to a thin yogurt or ayran. It is made by inoculating the milk of cows, goats, or sheep with kefir grains, which are colonies of bacteria and yeast that ferment the milk. The word "kefir" is believed to have originated from the Turkish word "keyif," meaning "pleasure" or "good feeling," referring to the sensation one might get after drinking it. Kefir has a tart and tangy flavor with a slightly effervescent or carbonated quality due to the fermentation process. It is consumed widely in Western Asia and Eastern Europe, often as part of meals. The drink is known for its probiotic content, which includes a variety of beneficial bacteria that promote gut health. In summary, kefir means:

• A fermented milk drink made with kefir grains.
• A drink with a tangy, sour taste and slight effervescence.
• Its name derives from a Turkish word meaning "pleasure" or "good feeling" associated with drinking it.

It is valued both as a traditional food and for its potential health benefits related to digestion and gut microbiota.