-ræður

From Old Norse -rǿðr. Underwent an apophony (substitution of one root vowel for another) from the suffix -rað in hundrað (“a hundred”).^[1] Compare the Icelandic hundrað, Latin ratiō (“reason, calculation”), reor (“I reckon, calculate; I think, deem, judge”) and ratus (“established, authoritative; fixed, certain”).^[1]

• (dated, archaic) -rœður, -rœðr^[1]

-ræður (feminine -ræð, neuter -rætt, comparative -ræðari, superlative -ræðastur)

1. of age, height or depth

   ‎átta (“eight”) + ‎-ræður → ‎áttræður (“eighty years old”)

2. of height or depth

   ‎tólf (“twelve”) + ‎-ræður → ‎tólfræður

• Compound adjectives referring to someone's age or by some unit (of measurement) are composed of either -tugur (20-70s, 90s archaic/obsolete) or -ræður (80s-100s, 70s archaic/obsolete). The adjective tólfræður is only used to refer to something by a unit, not a person by age.

• -ræði
• ræðinn
• -ræðni

Compare ræða (“to speak, to talk, to discuss”).^[1]

• (dated, archaic) -rœður, -rœðr^[1]

-ræður (feminine -ræð, neuter -rætt, comparative -ræðari, superlative -ræðastur)

1. used in compounds; spoken of

• fjölræður (“much spoken of”)