Lower-class names the social group with less money, less power, and usually less formal education than other groups. In older books it sat under middle-class and upper-class, as if society were a tidy ladder. Today many people treat the word as offensive: it can sound as if you are ranking human worth, not describing a situation. News and careful speakers more often say working-class, low-income, or talk about people with less money, depending on what they mean. If you meet lower-class in an old novel, that is the ladder idea. If you use it about a living person now, it can land as a snub. Though actually, even 'class' talk is messy — countries do not draw the lines in the same place, and people inside a group may refuse the label.