Usage: 5 forms in 16 verses
Form Translated As     In Verse(s)
αρρωστίασ infirmity LXX.2Kgs.1.2
my illness LXX.2Kgs.8.8LXX.2Kgs.8.9
sickness LXX.2Chr.21.15
αρρωστίαν with his illness LXX.2Kgs.13.14
αρρωστίαισ sicknesses LXX.2Chr.21.15LXX.2Chr.21.19
αρρωστία αυτού his infirmity LXX.2Chr.16.12
αρρωστία a sickness LXX.2Chr.21.18LXX.Eccl.5.13
his illness LXX.Ps.41.3
his sickness LXX.2Chr.21.19
illness LXX.1Kgs.17.17
sickness LXX.Eccl.5.16LXX.Eccl.5.17LXX.Eccl.6.2

Liddell-Scott-Jones

ἀρρωστία (arrōstia) illness G:N-F

ἀρρωστία-ία, ,

weakness, sickness, [Refs 5th c.BC+]: especially lingering ailment, bad state of health, [Refs 5th c.BC+]

__2 moral weakness, [Refs 4th c.BC+]; loss of morale, [Refs 5th c.BC+] lack of eagerness to serve, [Refs 5th c.BC+]