conjunction
but, however
A1
aber is a coordinating conjunction meaning 'but' or 'however'. It connects clauses without changing word order (unlike subordinating conjunctions) and doesn't send the verb to the end. It links contrasting information; punctuation usually follows standard comma rules but a comma is not required before aber.
Examples
Das Wetter ist schön, aber es ist kalt.
The weather is nice; however, it's cold.
Der Plan war gut, aber das schlechte Wetter verhinderte die Umsetzung, sodass die Veranstaltung verschoben wurde.
The plan was good, but the bad weather prevented its implementation, so the event was postponed.
Ich wollte kommen, aber ich war krank.
I wanted to come, but I was ill.
Details
Mnemonics
Imagine two contrasting ideas with a small bridge labeled 'aber' between them
sounds like English 'aber' — close to 'but' in rhythm
n/a
Notes
'Aber' is a coordinating conjunction and does not change word order (it does not send the verb to the end).