ـتر

From Proto-Iranian *-tarah, from Proto-Indo-Iranian *-taras, from Proto-Indo-European *-teros.

• IPA^(key): /tɪɾ/

ـتر (-tir)

2. a suffix forming the comparative degree of an adjective

• ـترین (-tirîn)

Inherited from Middle Persian [Book Pahlavi needed] (-tl /⁠-tar⁠/), from Proto-Iranian *-tarah, from Proto-Indo-Iranian *-taras, from Proto-Indo-European *-teros.

ـتر • (-tar)

2. a suffix forming the comparative degree of an adjective
3. (no longer productive) a suffix forming the relational of a noun; X-kind/-type

• ـترین (-tarin)

• MacKenzie, D. N. (1971) “-tar”, in A concise Pahlavi dictionary, London, New York, Toronto: Oxford University Press, page 82
• Mayrhofer, Manfred (1986) Etymologisches Wörterbuch des Altindoarischen (in German), volume 2, Wiesbaden: Dr. Ludwig Reichert Verlag, page 736:

  ‑tā́ra-: Suffix zur Bildung des Komparativs/Relationals in Altiranisch und Altindisch (Avestisch ‑tara, Sanskrit ‑tara, Altpersisch ‑tara). In Neu‑Persisch nur noch produktiv in Komparativen (biš‑tar, kam‑tar etc.) und ansonsten fossil erhalten im Substantiv jowdar ‘Roggen’ < jow ‘Gerste’ + tar.

  ‑tā́ra‑: Suffix for forming comparatives/relational nouns in Old Iranian and Old Indic (Avestan ‑tara, Sanskrit ‑tara, Old Persian ‑tara). In New Persian it remains productive only in comparatives (biš‑tar, kam‑tar etc.) and is otherwise preserved as a fossil in the noun jowdar ‘rye’ < jow ‘barley’ + tar.