Sentence:  When they got home Harold was grateful for the stillness in the <WSD>apartment</WSD> , and thought how , under different circumstances , they might have stayed on here , in these old-fashioned , high-ceilinged rooms that reminded him of the Irelands ' apartment in the East Eighties . 
Meaning of the word marked with <WSD> tags:  a suite of rooms usually on one floor of an apartment house