as·the·ni·a 
(ăs-thēnē-ə)
(ăs-thēnē-ə)n.
Loss or lack of bodily strength; weakness; debility.
[New Latin, from Greek astheneia, from asthenēs, weak : a-, without; see A-1 + sthenos, strength; see segh- in the Appendix of Indo-European roots.]