Middle-class and Upper-middle-class

Middle-class adjective - Occupying a socioeconomic position intermediate between those of the lower classes and the wealthy.

Upper-middle-class and middle-class are semantically related. In some cases you can use "Upper-middle-class" instead an adjective phrase "Middle-class".

Upper-middle-class adjective - Occupying the upper part of the middle socioeconomic range in a society.

Middle-class and upper-middle-class are semantically related. You can use "Middle-class" instead an adjective phrase "Upper-middle-class".