-дей

• -дай (-dai), -тей (-tei), -тай (-tai), -ндей (-ndei), -ндай (-ndai)

Possibly inherited from Proto-Turkic *-layu (“similative suffix”), however phonetic change from /l/ to /d/ is unexplained.

Compare Tatar -дәй (-däy), Kyrgyz -дей (-dey), Southern Altai -дий (-diy), Bashkir -дәй (-dəy), Uzbek -day.

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)

-дей • (-dei)

1. -like (Used to show resemblance to the noun.)

   ‎бөрі (börı, “wolf”) + ‎-дей (-dei) → ‎бөрідей (börıdei, “like a wolf, wolf-like”)

   Ол маған қарындастай. ― Ol mağan qaryndastai. ― She is like a sister to me.

2. (with -ген (-gen) or -етін (-etın) participles) as, as if, like

   Сіз көріп тұрғаныңыздай... ― Sız körıp tūrğanyñyzdai... ― As you can see...

   Цезарь айтқандай: "Келдім, көрдім, жеңдім".... ― Sezar aitqandai: "Keldım, kördım, jeñdım".... ― As Caesar said: "I came, I saw, I conquered"

   Мен күлетіндей күл! ― Men kületındei kül! ― Laugh like I do!

3. (with -етін (-etın) participle) Shows the purpose or the result of the verb.

   Ол мен еститiндей қатты сөйледі. ― Ol men estitindei qatty söiledı. ― She spoke so loudly that I could hear.

• -дѣ́й (-dě́j) — Pre-reform orthography (1918)

Combining form of де́ять (déjatʹ, “to do”), Inherited from Old East Slavic дѣꙗти (dějati), from Proto-Slavic *dějati, an extension of Proto-Slavic *děti (“to do, to say”) (whence деть (detʹ)), from Proto-Balto-Slavic *dḗˀtei, ultimately from Proto-Indo-European *dʰeh₁- (“to do”).

-де́й • (-déj)

1. Suffix added to stems to show that it does something; a doer.

   ‎ча́ры (čáry, “magic”) + ‎-дей (-dej) → ‎чароде́й (čarodéj, “magician, sorcerer”)

   ‎ли́хо (líxo, “evil”) + ‎-дей (-dej) → ‎лиходе́й (lixodéj, “evildoer”) (poetic)

• -тель (-telʹ), -арь (-arʹ), -ник (-nik), -ец (-ec) (suffixes for "a doer")