marriage

Examples-

monogamy:  one marriage at a time
polygamy: married to several people at the same time

rich

Exmples-                                                      plutology:  the study of wealth
plutologist:  an expert in the study of wealth

extreme

Examples-

ultraism:  extreme beliefs                                   
ultramodern:  extremely modern

skin

Examples-

dermic:  having to do with the skin
dermoid:  resembling skin                                            dermatology:  the study of the skin

circle or cycle

Examples -

~Note: transportation is important (think wheel)
motorcycle:  a cycle having a motor
cyclic:  having a cycle or circle
cycloid:  resembling a circle or cycle