A/de/em is 3 the most commonly used preposition in portuguese, below ordinal introducing their meaning and usage.

① A: Represent way, general interpret arrives for ＂ ＂ .
A Beijing (go to Beijing)

② De: Have two meanings.
The first meaning expresses all, general interpret is the ＂ of ＂ .
鉶 of O Carro De Jo (be like the car that hold high. If hold high,be familiar Portuguese man name, the John that is equivalent to English)
The 2nd meaning represents starting point, general interpret is ＂ from ＂ .
Eu Sou De China. (I come from China, namely I come from China)

③ Em: Show a location, general interpret is in for ＂ ＂ .
Eu Estou Em Portugal. (I [temporarily] be in Portuguese)

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