Viriya: 'energy', lit. 'virility', 'manliness' or 'heroism' from vīra man, hero; Lat. vir cf. virtus is one of the 5 spiritual abilities and powers see: bala one of the 7 factors of enlightenment see: bojjhanga and identical with right effort of the 8-fold path.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.