-ı

From Ottoman Turkish ـی (-ï, “accusative case marker”), itself from either Proto-Common Turkic *-g, *-ïg (“accusative case marker”) or simplified from Proto-Common Turkic *-nï (“accusative case marker”) to suit where oblique case is unnecessary for the accusative case, since the oblique case *-n- is not productive by itself and requires other cases. Compare Old Turkic 𐰍 (ǧ /⁠-(ï)ɣ⁠/), 𐰃𐰍 (iǧ /⁠-ïɣ⁠/).

-ı

1. definitive accusative suffix

   Seni seviyorum ― I like you

   Kitabı istiyorum ― I want the book(accusative used)

   Kitap istiyorum ― I want a book(accusative not used)

• It becomes -yı if the word ends with a vowel.
• It becomes -nı when preceded by third person singular possessive suffix -ı.

• -i
• -nı

From Ottoman Turkish ی (-ï, “possessive marker”), from Proto-Turkic *-ï (“possessive marker”). Cognate with Old Turkic 𐰃 (i /⁠-ï⁠/).

-ı

1. 3rd person singular possessive suffix

• Although it is believed to become -sı when the word ends with a vowel, this suffix probably comes from a different root.

• -i

From Ottoman Turkish ی (-ï, “adverbial suffix”), from Proto-Turkic *-u. Cognate with Old Turkic 𐰆 (u /⁠-u⁠/).

-ı

1. (unproductive and limited to certain pattern and copula) Makes adverbs out of verbs

• -i
• -u
• -yı

• -u, -i, -ü

From Ottoman Turkish ی (-ï), from Proto-Turkic *-ïg.

-ı

1. Suffix creating nouns out of verbs

   ‎tak- (“to put on, attach”) + ‎-ı → ‎takı (“ornament, jewellery”)

   ‎say- (“to count”) + ‎-ı → ‎sayı (“number”)