cannon
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cannon
A large, heavy gun that was formerly used mainly in wars and for defending fortresses to fire projectiles over long distances.
Auf der alten Burgmauer stehen noch mehrere historische Kanonen.
Several historic cannons are still standing on the old castle wall.
You can tell from the context whether the literal or a figurative meaning is intended. If the topic is history or the military, it usually refers to the weapon. In everyday, colloquial situations, it is often one of the idioms.
Auf der Festung kann man noch alte Kanonen besichtigen.
At the fortress, you can still view old cannons.
In the literal sense, 'Kanone' (cannon) is often used with verbs such as 'abfeuern' (to fire), 'laden' (to load), or 'richten auf' (to aim at), which describe a military or historical action.
Die Soldaten luden die Kanone für den Salutschuss.
The soldiers loaded the cannon for the salute.
The expression 'eine Kanone sein' (to be a whiz) is used with the preposition 'in' followed by the dative to name the area of expertise. The person is always the subject of the sentence.
Mein Bruder ist in Mathe eine echte Kanone.
My brother is a real whiz at math.
The expression 'unter aller Kanone' (absolutely terrible) is a fixed idiom and is not changed. As a predicative noun phrase, it describes a thing or performance that is extremely bad.
Das Essen in der Kantine war heute unter aller Kanone.
The food in the cafeteria was absolutely terrible today.
The idiom 'mit Kanonen auf Spatzen schießen' (to use a sledgehammer to crack a nut) works like a normal verb in a sentence. It describes someone reacting to a small problem with excessive effort.
Für diese einfache Aufgabe ein ganzes Team einzusetzen, heißt mit Kanonen auf Spatzen schießen.
Using an entire team for this simple task means using a sledgehammer to crack a nut.
expert
'der Experte' and 'eine Kanone sein' can both express that someone is very good in a particular area. 'der Experte' is neutral and fits factual situations, for example at work, in the media, or when dealing with specialist questions. 'eine Kanone sein' (to be a whiz) is colloquial and stronger: it sounds admiring and means that someone is exceptionally good. Learners may confuse the words because both describe a capable person. If you want to talk neutrally about specialist knowledge, use 'Experte'. If you are speaking casually and very positively about strong performance, 'Kanone' is more likely to fit.
Im Schach ist Lena wirklich eine Kanone.
Lena is a real whiz at chess.
Nach dem Vortrag beantwortet der Experte noch Fragen zum neuen Gesetz.
After the talk, the expert answers more questions about the new law.