Sunt verba voces quibus hunc lenire dolorem possis, magnam morbi deponere partem → Words will avail the wretched mind to ease and much abate the dismal black disease.
necessary: P. and V. ἀναγκαῖος.
if it is needful: P. and V. εἰ δεῖ, εἴ τι δεῖ.
what is needful: P. and V. τὸ δέον, τὰ δέοντα.
lacking: P. and V. ἐνδεής, P. ἐλλιπής.