ἀυδρία

English (LSJ)

ἡ, = ἀνυδρία, Pl.Lg.844a, Thphr.HP8.6.6.

Spanish (DGE)

-ας, ἡ
sequía, aridez τισι τόποις σύμφυτος Pl.Lg.844a, χώρας Thphr.HP 8.6.6, BE 1976.267 (Esparta III a.C.?); cf. ἀνυδρία.

German (Pape)

[Seite 391] ἡ, = ἀνυδρία, v.l. Plat. Legg. VIII, 844 a. S. Lob. Phryn. 729.

Russian (Dvoretsky)

ἀϋδρία: ἡ Plat. v.l. = ἀνυδρία.

Greek (Liddell-Scott)

ἀϋδρία: ἡ, = ἀνυδρία, Πλάτ. Νόμ. 844Α, Βεκκ.

Greek Monolingual

ἀϋδρία, η (Α)
η ανυδρία.

ἀϋδρία/ἀυδρία

ἀϋδρία or ἀυδρία? And there's the additional complication of those ancient (usually late) authors who spell it (properly, they thought) with the movable nu, since the alpha privative occurs before a vowel (ἀνυδρία, "lack of water"). As for ἀυδρία vs. ἀϋδρία, Plato manuscripts show the former, Theophrastus manuscripts (Historia plantarum 8.6.5.2) the latter. Plato and Theophrastus had no diaeresis-sign, and no need for it, so it's really a question of taste for medieval scribes. My preference would be for the most simple: ἀυδρία.

Additional observation: the disappearance in late antiquity of the initial rough breathing (dasia) of ὗδωρ, "water," might have inspired the need for the insertion of nu-movable — so an-ydria instead of the former a-hydria. The same could perhaps be said of the medieval scribe(s) of Theophrastus, for whom the diaeresis was a necessary sign that the now-unaspirated upsilon did not make a diphthong with the preceding alpha. Bill Berg