En (Cyrillic)

En (Н н; italics: Н н) is a letter of the Cyrillic script.
It commonly represents the dental nasal consonant /n/, like the pronunciation of ⟨n⟩ in "neat". And it can be palatized /nʲ/ like in the pair of hard and soft consonnant for the word: жена́ [ʐɨˈna] 'wife' and же́нин [ˈʐenʲɪn] 'wife's'.
The capital Cyrillic letter En looks the same as the capitals Greek letter Eta (Η η) and Latin letter H. As with most Cyrillic letters, the lowercase form is simply a smaller version of the uppercase. However, in modern Church Slavonic publications, the old N-shaped form is still often used.
It should not be confused with the letter И (similar to a mirrored shape of the Latin letter N):
In the Early Cyrillic alphabet, the letter was created according to the model of the Greek letter Nu. The modifications of the glyph N over the centuries have led to the adoption of the current form of Greek letter Eta (H), a shape that has been formerly used as a model for the letter И.
The believing that "the reason En has a horizontal bar, like H, instead of a diagonal line, is to avoid confusion with the letter И" has no groundings:
It seems more probable that the change of shapes in Cyrillic resulted from a cascade of consequences, apparently around the letter И, and maybe also letter І and the letter П (see these letters for details of their history).
From c. 893 in Bulgaria, the Early Cyrillic alphabet was made of uncial Greek letters and glagolitic letters. This Cyrillic uncial, called "Ustav (script) [ru]" in Russian, is a style developed on the model of the Greek uncial.
The name of En was нашь (našĭ), meaning "ours". The letter was created according to the model of the Greek letter Nu (Ν ν) as they share the same sound /n/. Therefore, the letter had a descending diagonal "\" between the two vertical lines.
At the same time, the letter И was created according to the model of the Greek letter Eta (Η η) for the same reason (sound /i/). Therefore, the letter had a horizontal line "-" between the two vertical lines.
In Cyrillic uncial style (as in Greek), for the two letters Н and И (shapes N and H), the vertical columns are drawn wide and the line between is thin.
These shapes are mainly used up to the 13th century, and since the 19th century, in academic publishing to reproduce old Slavonic texts (when ustav-style Cyrillic fonts are used). See for example:
The letter И like an H can still be seen in a book "Arithmetic" from Leonty Magnitsky published in Moscow in 1703 (see the book ШИЦГАЛ А.Г., РУССКИЙ ТИПОГРАФСКИЙ ШРИФТ, page 24), or in a book printed by order of the Tsar in 1706 (see Font of I.Kopievich in the Russian version of the article Civil script [ru]).
In the Cyrillic letter Н with the Greek shape N, the descending diagonal "\" will progressively become shorter:
See for example:
One of the explanations may be the management of the virtual line horizontally dividing the letters as А,Б,В,Є,Ж,З,Н,К,Х,Ч,Э,Ю. And this was also applied to the glyph N for some unknown reason (maybe a need for simplification, or to create a styling effect). For example, the scribe draws the horizontal in the glyph H higher than the middle, then the other similar letters will be drawn with a virtual line higher. Therefore, in the glyph N, the scribe must shorten the diagonal and make it end at the level of the virtual line. Then, other scribes repeat the same modifications but sometimes without respecting the same virtual line for all the letters, thus making the root cause disappear.
In uncial Greek, the shape of the letter H sometimes sees the horizontal line rise upwards, and the shape of the letter N either does not change, or moves accordingly, and sometimes we can see both versions in the same text (see Lectionary 5 and Lectionary 183).
From the 15th century, the poluustav [ru] (en in Russian) a semi-uncial style developed, and is notably still used today by the Church Slavonic publishing. This style turns into a more fluid writing: there is a slope, letters descending below the line, capital letters, transitional cursive.
In parallel, the first printing fonts are being developed. In 1517, a work of simplification and "romanization" of the Cyrillic alphabet by the first Belarusian printer François Skorina (Prague and Vilnius editions) will give a writing of capitals close to modern. This font was further improved thanks to the Belarusian printer Ilya Kopievich, who from 1700 to 1706, by order of Peter I, published about 25 books in Amsterdam and Danzig. The font of his publications was extremely close to the civil font adopted by the Russian emperor and printed by Pierre Mogiloy in 1708.
In the Cyrillic И with the Greek shape H, the horizontal line "-" has become an ascending diagonal:
See for examples:
Therefore, the H-shape for the letter И became less frequent and eventually became available for another letter as... Н. Then the official Civil Script made it mandatory to use the H-shape for the letter Н (in use at that time, see Karion Istomin's alphabet book from 1694) at the detriment of the original N-shape. No specific explanation is available for this choice and if there was a problem with readability, it could have been decided to return to the original shape as in the Greek or Latin alphabet. We can only note that the Church prefers to continue using the old shape, thus refusing to reverse two ghlyphs in the Cyrillic alphabet created specifically to translate the Bible, and thus avoiding repeating the instability of this H-shape (cf. cursive).