conjunction
whether, if
B1
'ob' is a subordinating conjunction meaning 'whether' or 'if' in indirect yes/no questions. Use it to introduce subordinate clauses and it sends the finite verb to the clause end (verb-final word order). Not interchangeable with 'wenn' for conditionals. No reflexivity or auxiliary; not a preposition.
Examples
Ich weiß nicht, ob er heute kommt.
I don't know whether he'll come today.
Der Chef fragte, ob die Lieferung pünktlich angekommen war, weil Kunden bereits warteten.
The boss asked whether the delivery had arrived on time because customers were already waiting.
Frag sie, ob sie mitkommen will.
Ask her if she wants to come along.
Details
Mnemonics
a small question mark hovering over the word to signal doubt/choice
sounds like 'awb' — think of someone asking 'Aw, but will it work? — whether or not'
Notes
Subordinating conjunction used to introduce indirect yes/no questions and clauses expressing doubt. Word order in the subordinate clause places the finite verb at the end.