There are a number of languages which have historically been written in more than one alphabet (Hindi/Urdu, Serbo-Croatian, Uzbek and so on). I am wondering which single language has been regularly written in the most different alphabets.
My bet is on another Turkic language, Uighur, especially if we use it to mean both modern Uighur and its ancestor Old Turkic, which was the official language of the Uighur Khaganate (begun in 742) and later the predominant language of Turfan / Turpan, East Turkestan (Xinjiang province, China), where Uighurs settled in 840 and have remained to the present day.
According to the UCLA Language Materials Project, the earliest Uighur texts are written in three scripts: the Old Turkic runes (also called Orkhon-Yenisei runes), the Manichean script and the Uighur script. All three types probably ultimately go back to Aramaic script. (The Aramaic script derives from Phoenician, as do a plurality of the world's orthographies eventually.)
The Uighur script derived from the Sogdian alphabet (Ancientscripts). Sogdian was a Middle Iranian language related to Pahlavi. By the seventh century, Sogdian merchants had a strong presence along the Silk Road (Jonathan Skaff), from their origin in Samarkand all the way to the oasis state of Turfan, where many of them came to settle. In 840 the Uighurs came here too, and they eventually adopted the script.
The oldest Uighur inscription known, from 732, is from the Orkhon river basin, central Mongolia, in Old Turkic runes, which were possibly based on the Sogdian script or the Chinese script, but there is a powerful argument for a tamga origin too. Tamga is Mongolian for "stamp" or "seal," and the use of Tamgas throughout Eastern Eurasia to differentiate clans from each other, for marking property, for official correspondence and for graves goes back to prehistory.
The Manichean script coexisted along the Silk Road with the Sogdian; it is so called because adherents of the Manichean religion seemed to prefer it, and it is said that Mani himself may have devised it. Uighur documents in the Manichean script were found at Turfan by German excavators in the late nineteenth century.
Excavations at Turfan have found Uighur documents written in the Syriac, Tibetan, Brahmi, Nestorian, and Estrangelo scripts; 'Phags-pa may have been used as well. Assumedly, writing Uighur in these scripts was an at least somewhat regular occurrence throughout the Tarim basin at various times, the preferences changing from 840 to the 1300s and beyond. This document by Doug Hitch outlines the basic features dozens of variants of writing systems used in Central Eurasia, not all for Uighur.
Uighur gradually came to be written predominantly in the Chagatai script, a variant of the Arabic script used originally for the extinct Turkic language Chagatai, which was then widely spoken throughout Central Eurasia.
In the 1920s, some Uighur-speaking regions became part of the Soviet Union, and others came under its influence, and at first the Soviet Union tried to Romanize the Uighur script, but then decided to use a Cyrillic-derived alphabet known as Uyghur Siril Yëziqi instead.
In the 1950s, the Chinese promoted the use of Yëngi Yëziqi, a mixture of Pinyin (Latin-derived) and Cyrillic, for Uighur. Its predominant usage lasted about ten years.
The most commonly used, and official, Uighur script today is Uyghur Ereb Yëziqi, a newer Arabic-derived script.
Some of the Uighur people have pressed for a change to a Latin-based script known as Uyghur Latin Yëziqi instead, for ease of use with information technology. Many Uighurs know both this script and the Ereb Yëziqi.
I think the answer may be: Ottoman Turkish.
In the twentieth century alone, it could be found regularly written in the Arabic, Greek, Armenian, Hebrew and Syriac alphabets. And, since the language reforms of the 1930s happened after the alphabet reform of 1928, we can add the Latin alphabet to that list. I think there were Ottoman Turkish books published in Bulgaria using the Cyrillic script as well.
That makes at least six –and possibly seven– alphabets.
I think it is Sanskrit, which has been written in a large number of Asian scripts plus Latin. See
for a graphic of 17, which I suspect is not all.
A possible answer may be Mongolian. Alphabets used are: Mongolian script (traditional, Galik, Vagindra, Todo), Phags-pha, Soyombo, Chinese Hanzi, Arabic, Latin, Cyrillic.
Mongolian in literature involved a lot of vocabulary originated from foreign languages like Sanskrit, Tibetan and Chinese which is why Galik alphabets where used at the time. However, everyday Mongolian uses most of these alphabets, because some dialects like Khalkha (official dialect of Mongolia) uses sounds not originally inclusive in the traditional script. Vagindra is the name for the Mongolian script with Buryat dialect-specific alphabets while Todo or Clear script is the one for Oirat dialects. Vagindra had been used and Todo is still officially used in Mongol autonomies in Xinjiang.
Phags-pha was created by a Tibetan scholar in service of Kublai Khan. It was created on a decree by the Khan. This script was intended to be used officially by the Mongols. However, it had only been used extensively in the court thus there are a lot of documents written in Phags-pha. The alphabets are still used in Mongolia and Tibet for decorative, artistic and religious purposes.
Soyombo was created by Zanabazar, a noble khutagt. Late Bogd Khan of Mongolia was the last reincarnated avatar of him. The script is still used extensively in the temples. Also, the first letter in the alphabet made national symbol for Mongolia.
It is evident that Chinese Hanzi was used for writing Mongolian by transliterating the language. A famous book from the Middle Ages (The Secret History of the Mongols) was first found in a Mongolian edition written using Chinese Hanzi characters.
Arabic and Persian alphabets where used by the Mongol Empire's presence in the Middle East and the later Ilkhanate dynasty. There are many written documents including stamps and paizs (modern-day passport) issued by Mongol khans and nobles and letters to Pope and other European entities.
Ossetic: first in Greek script; then in Church Slavonic script; then (in South Ossetia) Georgian script; then in amplified Cyrillic (Russian script with several newly invented characters); then Latin script; then simple Cyrillic script (Russian script with only one special sign: æ). Six alphabets, not bad for a still living language.
It's probably not a record holder, but to be precise with Bosnian/Croatian/Serbian, it has been written in the Latin, Cyrillic (both in the standard form and in an extinct, western form called Bosančica), Glagolitic, and Arabic (the so-called Arebica). Arebica saw use until WWII, Bosančica seems to have gone extinct by the 18th century, and Glagolitic for the vernacular was probably extinct by the end of the 18th century---Glagolitic for Croatian Church Slavonic lasted until 1927, albeit with partial use lasting until Vatican II.
Kurdish has been written in the Arabic alphabet, in the Latin alphabet, in the Cyrillic alphabet, Kurdish has even been written in the Armenian alphabet in Soviet Armenia.
Originally, Gagauz was written in the Greek alphabet. Then, it has been written in Cyrillic letters, and then in Latin letters.
Ancient Uzbeks who were know as part of Turkic tribes were using Turkic alphabet
Which is totally dead nowadays.
When Islam came to Turks they start using Arabic alphabet. But as there are some letters such as "P", "Ж"-Cyrillic, in Uzbek as are in Persian. That made it same as Persian alphabet, which was so similar to Arabic. In the time of Soviet Union Uzbeks began using Cyrillic and since independence They are using both Cyrillic and Latin