Sentence:  A thing of beauty is a joy for ever: / Its <WSD>loveliness</WSD> increases; it will never / Pass into nothingness; but still will keep / A bower quiet for us, and a sleep / Full of sweet dreams, and health, and quiet breathing. 
Meaning of the word marked with <WSD> tags:  The property of being lovely, of attractiveness, beauty, appearing to be lovable.