
das Ass
ace
The playing card with the highest or lowest value in many card games, usually marked with the symbol A.
Beim Skat ist das Kreuz-Ass der höchste Trumpf.
In Skat, the ace of clubs is the highest trump card.
ace
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ace
The playing card with the highest or lowest value in many card games, usually marked with the symbol A.
Beim Skat ist das Kreuz-Ass der höchste Trumpf.
In Skat, the ace of clubs is the highest trump card.

ace
A person who is exceptionally good and successful in a particular field; an expert or highly skilled person.
Er ist ein echtes Ass in Physik und löst jede Aufgabe.
He is a real ace in physics and can solve every problem.

ace
In sports, especially tennis or volleyball, a serve that the opponent cannot reach or return according to the rules and that leads directly to a point.
Die Spielerin servierte im entscheidenden Moment ein Ass.
The player served an ace at the decisive moment.
Careful: 'das Ass' (ace) has nothing to do with the English vulgar word 'ass.' In German, it is either neutral (a playing card) or positive (an expert, a point in sports). Confusing the two is a very common mistake.
Mit vier Assen auf der Hand hat er das Spiel gewonnen.
With four aces in his hand, he won the game.
When 'Ass' describes a person who is very good at something, use the preposition 'in' followed by the dative to name the field.
Meine Schwester ist ein Ass in Mathematik.
My sister is an ace in mathematics.
Calling a person an 'Ass' (ace) is colloquial. In formal or written contexts, you would more likely use words such as 'Experte' (expert) or 'Könner' (skilled person).
Frag mal Paul, der ist ein echtes Ass bei Autoreparaturen.
Ask Paul—he's a real ace at car repairs.
In a sports context, especially in tennis or volleyball, 'Ass' is combined with the verbs 'schlagen' (to hit) or 'servieren' (to serve).
Der Tennisspieler hat im letzten Satz drei Asse geschlagen.
The tennis player hit three aces in the last set.
professional / pro
Profi can refer to someone who does an activity professionally or is very competent at it. Ass, by contrast, emphasizes that someone is exceptionally good and successful in a particular area. Profi fits when referring to professional status or reliable competence, while Ass is used for outstanding skill.

Mit seinen mehrfach ausgezeichneten Aufnahmen ist Leon ein echtes Ass im Umgang mit der Kamera.
With his award-winning photographs, Leon is a real ace at handling a camera.
Als bezahlter Fotograf ist Leon ein Profi im Umgang mit der Kamera.
As a paid photographer, Leon is a pro at handling a camera.