<span style="color:#800080;">1-He lives under us.</span><br/><br/><span style="color:#ff0000;">2-He lives directly under us.</span><br/><br/><span style="color:#800080;">3-He lives below us.</span><br/><br/><span style="color:#ff0000;">4-He lives directly below us.</span><br/><br/>If we are living in the apartment 5A in which case:<br/><br/>a-He lives in 4A.<br/><br/>b-He lives on the fourth floor but could be living in any of the apartments.<br/><br/>c-He lives in an "A" apartment but could be on any of the floors below us (4, 3, 2 ...)