In Slavic languages, iotation (, ) is a form of palatalization that occurs when a consonant comes into contact with a palatal approximant from the succeeding phoneme. The is represented by iota (ι) in the Cyrillic alphabet and the Greek alphabet on which it is based. For example, ni in English onion has the sound of iotated n. Iotation is a phenomenon distinct from Slavic first palatalization in which only the front vowels are involved, but the final result is similar. Sound change Iotation occurs when a labial (, ), dental (, , ) or velar (, , ) consonant comes into contact with an iotified vowel, i.e. one preceded by a palatal glide . As a result, the consonant becomes partially or completely palatalized. In many Slavic languages, iotated consonants are called "soft" and the process of iotation is called "softening". Iotation can result in a partial palatalization so the centre of the tongue is raised during and after the articulation of the consonant. There can also be a complete sound change to a palatal or alveolo-palatal consonant. This table summarizes the typical outcomes in the modern Slavic languages: According to most scholars, the period of iotation started approximately in the 5th century, in the era of Proto-Slavic, and it lasted for several centuries, probably into the late Common Slavic dialect differentiation. Here are examples from the early stage: Proto-Slavic * > Russian, Ukrainian, Macedonian, Bulgarian , Czech , Serbo-Croatian Orthography Iotified vowels In Slavic languages, iotified vowels are preceded by a palatal approximant before a vowel, at the beginning of a word, or between two vowels in the middle of a word, creating a diphthongoid, a partial diphthong. In the Greek alphabet, the consonant is represented by iota (ι). For example, the English apple is cognate to Russian яблоко (jabloko): both come from Proto-Indo-European stem *ābol-. As a result of the phenomenon, no native Slavic root starts with an or an but only with a and ; although other vowels are possible. As it was invented for the writing of Slavic languages, the original Cyrillic alphabet has relatively complex ways for representing iotation by devoting an entire class of letters to deal with the issue. There are letters which represent iotified vowels; the same letters also palatalize preceding consonants (with or without self-iotation), which is why iotation and palatalization are often mixed up. There are also two special