Escravidão vs. escravatura
The Portuguese words escravidão and escravatura both translate to "slavery," but their usage depends heavily on the region. In Brazil, escravidão is the universal term for all contexts. In Portugal, escravatura is preferred when discussing the historical institution or the trade, while escravidão is often reserved for the abstract condition of lacking freedom.
Escravidão
B2This is the primary term used in Brazilian Portuguese for the historical system, the trade, and the condition of being a slave. In European Portuguese (Portugal), this word is used less for historical contexts and more to describe the specific state of an individual or metaphorical situations, such as being a slave to a vice or debt.
A escravidão marcou profundamente a história do Brasil.
(Slavery deeply marked the history of Brazil.)
Ele diz que o trabalho excessivo é uma forma moderna de escravidão.
(He says that excessive work is a modern form of slavery.)
Muitos lutaram para fugir da escravidão nas fazendas de café.
(Many fought to escape slavery on the coffee farms.)
Ela vive na escravidão do vício em jogos.
(She lives in the slavery of gambling addiction.)
Escravatura
B2This term is the standard choice in European Portuguese (Portugal) and Lusophone Africa to refer to the historical institution, the transatlantic trade, and the collective system of slavery. To Brazilian ears, this word sounds archaic or overly formal and is rarely used in everyday speech.
Os navios transportavam vítimas da escravatura pelo oceano.
(The ships transported victims of slavery across the ocean.)
A abolição da escravatura em Portugal ocorreu no século dezoito.
(The abolition of slavery in Portugal occurred in the eighteenth century.)
O museu tem uma exposição sobre o fim da escravatura.
(The museum has an exhibition about the end of slavery.)
Discutiremos hoje o impacto econômico da escravatura nas colônias.
(Today we will discuss the economic impact of slavery in the colonies.)
Summary
In short, if you are speaking Brazilian Portuguese, use escravidão for everything. If you are speaking European Portuguese, use escravatura when talking about the historical system or trade, and escravidão when referring to the state of being unfree or in metaphorical contexts.