The word,,aber in German is most often used as a coordinating conjunction. Ich wollte nach Bremen fahren aber Mein Auto ist kaputt. Ich mag English aber es ist manchmal schwer. Aber used as a conjunction
When used as a coordinating conjunction, dont get its use confused with the word,, sondern. Two prerequisites must be met in order to use sondern. First, there must be contrast or opposite and second, there must be a negation of the main clause. Mein Vater ist nicht reich sondern arm. Die Kirche ist nicht alt sondern neu. Das ist nicht süß sondern sauer. My father is not rich but rather poor. The church is not old but rather new. That is not sweet but rather sour
When,,aber is used as a modal particle its meaning is not always easily converted into English. Das wird aber interessant! Boy, will that be interesting! That will really be interesting! Often, it is used to amplify the adjective that follows it. Used like this, it can be hard to translate into English. Das ist aber schade! Das ist aber wunderbar! Boy, that is a shame! / That is really a shame! Boy, that is wonderful! / That is really wonderful!
Aber can also take on the meaning of however when used as a particle. Das ist aber nicht mein Buch. That is, however, not my book. Das ist aber nicht mein Problem. That is, however, not my problem. Das ist aber nicht unsere Aufgabe. That is, however, not our assignment.
Aber can even be used occasionally as a noun. When used in this manner the meaning can vary greatly. Das Angebot hat ein Aber. The offer has a catch. Es gibt kein Aber! There are no ifs, ands or buts!