Portuguese language
The CPLP nations speak Portuguese with different accents. In some regions of Brazil (the country has 81% of the world's Portuguese-speakers), tu'("you" but used only to family and close friends) is not used as much as in Portugal. Also, regional slang can be found in different areas. The Portuguese Orthographic Agreement of 1990 (Acordo Ortográfico de 1990) tries to  get rid of some of the differences in spelling.