19th-century Changes
Throughout the 18th and 19th centuries, miscellaneous adjustments were made on an ad-hoc basis, as the Russian literary language came to assume its modern and highly standardized form. These included the introduction of the letter ё /jo/ (yo) and the gradual loss of ѵ (izhitsa, corresponding to the Greek upsilon and the Latin y), in favor of и (both of which represented /i/); and ѳ (corresponding to the Greek theta), in favor of ф or т. By 1917, the only two words still usually spelled with ѵ were мѵро (müro, "myrrh") and сѵнодъ (sünod, /sʲɪˈnod/, "synod"), and that rarely. The ѳ remained more common, though it became quite rare as a "Western" (French-like) pronunciation had been adopted for many words; for example, ѳеатръ (ḟeatr, "theater") became театръ (teatr, ). Attempts to reduce spelling inconsistency culminated in the standard textbook of Grot (1885), which retained its authority through 21 editions until the Russian Revolution of 1917. His fusion of the morphological, phonetic, and historic principles of Russian orthography remains valid to this day, though both the Russian alphabet and the writing of many individual words have been altered through a complicated but extremely consistent system of spelling rules that tell which of two vowels to use under all conditions.
Read more about this topic: Reforms Of Russian Orthography