faithless 0571 - apistos {ap'-is-tos}; from 0001 (as a negative particle) and 4103; (actively) disbelieving, i.e. without Christian faith (specially, a heathen); (passively) untrustworthy (person), or incredible (thing): -- that believeth not, {faithless}, incredible thing, infidel, unbeliever(-ing).
faithless 1169 - deilos {di-los'}; from deos (dread); timid, i.e. (by implication) {faithless}: -- fearful.
faithlessness 0570 - apaistia {ap-is-tee'-ah}; from 0571; {faithlessness}, i.e. (negatively) disbelief (lack of Christian faith), or (positively) unfaithfulness (disobedience): -- unbelief.