προστακτέον
From LSJ
Ἄξιόν ἐστι τὸ ἀρνίον τὸ ἐσφαγμένον λαβεῖν τὴν δύναμιν καὶ τὸν πλοῦτον καὶ σοφίαν καὶ ἰσχὺν καὶ τιμὴν καὶ δόξαν καὶ εὐλογίαν → Worthy is the Lamb that was slain to receive power, and riches, and wisdom, and strength, and honour, and glory, and blessing
English (LSJ)
A one must order, X.Hier.9.3; π. ὅπως . . Pl.R. 527c.
Greek (Liddell-Scott)
προστακτέον: ῥημ. ἐπίθ., πρέπει τις νὰ προστάξῃ, Ξεν. Ἱέρων 9. 3· πρ. ὅπως... Πλάτ. Πολ. 527C.
Russian (Dvoretsky)
προστακτέον: adj. verb. к προστάσσω.
Dutch (Woordenboekgrieks.nl)
προστακτέον, adj. verb. van προστάττω, er moet bevolen worden.