Ahnung vs. Vorstellung vs. Schimmer
The German words Ahnung, Vorstellung, and Schimmer all relate to having an idea, a clue, or an understanding of something, but they carry distinct nuances. The word Ahnung is your go-to term for general knowledge, facts, or a gut feeling. The word Vorstellung is used when dealing with mental images, concepts, or expectations. Finally, the word Schimmer is a highly informal term that literally means a glimmer, and it is almost exclusively used to emphasize a complete lack of knowledge.
Ahnung
The word Ahnung is the most common way to express having a clue, a hunch, or general knowledge about a fact or subject. It is extremely frequent in the negative phrase keine Ahnung, which is the standard way to say that you have no idea or do not know something.
Ich habe keine Ahnung, wo ich mein Auto geparkt habe.
(I have no idea where I parked my car.)
Sie hat wirklich viel Ahnung von klassischer Musik.
(She really knows a lot about classical music.)
Hast du eine Ahnung, wann der Zug abfährt?
(Do you have a clue when the train leaves?)
Er hatte schon so eine Ahnung, dass es regnen würde.
(He already had a hunch that it was going to rain.)
Wir haben nicht die geringste Ahnung, wie diese Maschine funktioniert.
(We do not have the slightest clue how this machine works.)
Wenn man keine Ahnung hat, sollte man besser schweigen.
(If one has no knowledge, it is better to stay silent.)
Vorstellung
The word Vorstellung refers to a mental image, a concept, or an expectation of how something is or should be. You use this word when you are picturing a situation in your mind, conceptualizing an abstract idea, or describing an assumption rather than just lacking factual information.
Ich habe eine genaue Vorstellung von meinem zukünftigen Traumhaus.
(I have a precise idea of my future dream house.)
Du machst dir keine Vorstellung davon, wie anstrengend die Reise war.
(You have no idea how exhausting the journey was.)
Seine Vorstellungen von einer guten Beziehung sind völlig unrealistisch.
(His concepts of a good relationship are completely unrealistic.)
Sie hatte eine ganz falsche Vorstellung von diesem Beruf.
(She had a completely wrong mental image of this profession.)
Haben Sie bereits eine Preisvorstellung für dieses Projekt?
(Do you already have a price expectation for this project?)
Es übersteigt meine Vorstellung, wie groß das Universum ist.
(It is beyond my comprehension how big the universe is.)
Schimmer
The word Schimmer literally translates to a glimmer or a faint light, but in the context of knowledge, it represents the tiniest spark of a clue. It is highly colloquial and is almost always used in negative expressions, such as keinen blassen Schimmer, to dramatically emphasize that you have absolutely zero knowledge about something.
Ich habe keinen blassen Schimmer, wovon du gerade redest.
(I do not have the faintest clue what you are talking about right now.)
Er hat keinen Schimmer, wie man einen platten Reifen wechselt.
(He does not have a glimmer of an idea how to change a flat tire.)
Wir hatten keinen Schimmer, dass sie heute Geburtstag hat.
(We had no clue that it is her birthday today.)
Davon habe ich wirklich absolut keinen Schimmer.
(I truly have absolutely no clue about that.)
Hast du auch nur den leisesten Schimmer, wer den Kuchen gegessen hat?
(Do you have even the slightest clue who ate the cake?)
Summary
To choose the right word, consider the type of knowledge you are referencing. Use Ahnung for general knowledge, facts, or hunches. Use Vorstellung when you are talking about a mental picture, an expectation, or a conceptual understanding. Reserve Schimmer for informal situations where you want to exaggerate your complete lack of knowledge, emphasizing that you lack even the faintest glimmer of a clue.