the state or quality of being weak; lack of strength, firmness, vigor, or the like; feebleness.

an inadequate or defective quality, as in a person's character; slight fault or defect

to show great sympathy for human weaknesses.

a self-indulgent liking or special fondness, as for a particular thing

I've always had a weakness for the opera.

an object of special desire; something very difficult to resist

Chocolates were her weakness.

noun

strength , strong point

noun

achilles heel * , appetite * , blemish , chink in armor , debility , decrepitude , deficiency , delicacy , enervation , failing , faintness , fault , feebleness , flaw , fondness , fragility , frailty , gap , impairment , imperfection , impotence , inclination , inconstancy , indecision , infirmity , instability , invalidity , irresolution , lack , languor , lapse , liking , passion , penchant , powerlessness , predilection , proclivity , prostration , senility , shortcoming , soft spot * , sore point , taste * , vice , vitiation , vulnerability , delicateness , flimsiness , fragileness , frailness , insubstantiality , puniness , unsoundness , unsubstantiality , weakliness , foible , weak point , appetite , partiality , preference , relish , accessibility , ailment , asthenia , atony , debilitation , defect , desirous , errability , exposedness , fallibility , ineffectiveness , inefficacy , invalidism , peccability , proneness , vacillation