HOU

hou(1)

hou(2)

hou(3)

hou(4)

后 = behind, back, after, last

后面 = hou(4)mian(-) = in the back, behind

Opposite of:

前面 = qian(2)mian(-) = in the front, ahead

后天 = hou(4)tian(1) = day after tomorrow, acquired (as opposed to congenital)

后天病 = hou(4)tian(1) bing(4) = acquired disease (as opposed to a congenital one)