Pronunciation: [fɹˈiːmɑːtˌɪn] (IPA) 
"Freemartin" is a term used to describe a sterile, female calf that is born as a twin with a male calf. The word is spelled "free-mahr-tin" and is pronounced [ˈfriː.mɑːtɪn] in IPA phonetic transcription. The "ee" sound is represented by the double "e" in the spelling, and the stress is on the first syllable with a long "i" sound. The second syllable has a short "a" sound and the final syllable has a similar sound to "tin".
A freemartin is a term used in veterinary medicine and livestock breeding to describe a female mammal, most commonly a bovine, that is sterile as a result of being born as a twin with a male sibling. Specifically, it refers to a female calf born alongside a male twin in cattle. It occurs due to the exchange of embryonic fluids between the twins during gestation, which leads to the mixing of their genetic materials.
The male hormones produced by the male twin affect the development of the freemartin's reproductive organs, leading to a variety of anatomical and physiological abnormalities. Typically, the reproductive tract of a freemartin is underdeveloped, rendering it incapable of reproduction. This condition is most commonly observed in cattle, although it has also been reported in other animal species such as goats and sheep.
Identifying a freemartin is usually based on external characteristics, such as having a larger size or masculine appearance compared to other female calves within the same litter. While freemartins cannot reproduce, they are typically healthy otherwise and can be raised for meat or used as work animals.
In livestock breeding, identifying freemartins is important as they cannot be used for breeding purposes, affecting the efficiency of the breeding program. However, freemartinism does not pose any significant health risks to the affected animals themselves.
The word "freemartin" originates from Old English, specifically from the combination of two words: "freo" meaning free or exempt from, and "mearðe" meaning a yearling heifer. In Old English, a freemartin referred to a female calf, born as a twin with a male calf, that is sterile and therefore considered exempt from future breeding. It is believed that the term has Anglo-Saxon roots and has been used in English since at least the 10th century.
