Copy/pasting from this official pdf from the Turkish government produces يانيه. Czech Wiki uses the same spelling. English Wikipedia and Wiktionary, however, both use the spelling یانیه. Those look identical on my browser but have different codepoints because one is using a ي and the other a ی.
Which one is right? Were ي and ی entirely interchangeable? or were their differing usage the result of different dialects, time periods, or some other criterion?
From what I know, Ottoman Turkish normally used ی which had the two dots when connected on the left and when connected on both sides, but when connected only on the right (at the end of the word) it usually had no dots. The grapheme ي was also sometimes used with exactly the same meaning, but when Arabic had the dotless ی in the word, so did Ottoman Turkish.
Osmanisch. Einführung in die Grundlagen der Literatursprache, 1999, Harrassowitz Verlag, Wiesbaden, by Korkut Bugday has it like this:
Am Wortende kann das ی (ye) mit oder ohne Punkte darunter geschrieben werden (sowohl die Schreibweise ي als auch ی ist möglich). Gedruckte osmanische Texte verzichten meistens auf die Punkte unter dem ی (ye). Bei arabischen Wörtern kann das ی (ye) am Wortende — dann immer ohne Punkte geschrieben — auch langes „a“ bezeichnen; ein solches ی (ye) bezeichnet man als elif maḳṣūre الف مقصورة (z.B. مصطفى Muṣṭafā).
In English:
At the end of the word, the ی (ye) can be written with or without dots underneath (both the spelling ي and ی are possible). Printed Ottoman texts usually omit the dots below the ی (ye). In Arabic words, the ی (ye) at the end of the word — always written without dots — can also indicate a long “a”; Such a ی (ye) is called elif maqṣūre الف مقصورة (e.g. مصطفى Muṣṭafā).
