Lower class and Socio-economic class

Lower class noun - The social class lowest in the social hierarchy.

Socio-economic class and lower class are semantically related. In some cases you can use "Socio-economic class" instead a noun phrase "Lower class".

Socio-economic class noun - People having the same social, economic, or educational status.

Lower class and socio-economic class are semantically related. Sometimes you can replace phrase "Lower class" with "Socio-economic class", this phrases are similar.