der Ritter
knight
In the Middle Ages, a mounted and armored warrior of noble or lower-noble origin who served a feudal lord.
Der Ritter zog sein Schwert, um die Burg zu verteidigen.
The knight drew his sword to defend the castle.

knight
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knight
In the Middle Ages, a mounted and armored warrior of noble or lower-noble origin who served a feudal lord.
Der Ritter zog sein Schwert, um die Burg zu verteidigen.
The knight drew his sword to defend the castle.

The adjective 'ritterlich' (chivalrous) is derived from the noun 'der Ritter' (knight). It describes honorable, polite, and protective behavior.
Es war sehr ritterlich von ihm, mir seinen Mantel anzubieten.
It was very chivalrous of him to offer me his coat.
In its original meaning, 'Ritter' (knight) is often combined with words from the Middle Ages, for example 'Burg' (castle), 'Rüstung' (armor), 'Schwert' (sword), or 'Turnier' (tournament).
Im Museum sahen wir die schwere Rüstung eines Ritters aus dem 14. Jahrhundert.
In the museum, we saw the heavy armor of a knight from the 14th century.
The fixed expression 'jemanden zum Ritter schlagen' (to knight someone) describes the ceremony in which a person is granted a title of nobility. This is still common in some monarchies today.
Der berühmte Schauspieler wurde für seine Verdienste von der Königin zum Ritter geschlagen.
The famous actor was knighted by the Queen for his services.
In the figurative meaning, the phrase 'ein wahrer Ritter' (a true knight/gentleman) is often used. It praises a man who behaves in an especially helpful and polite way.
Als er mir mit dem schweren Koffer half, war er ein wahrer Ritter.
When he helped me with the heavy suitcase, he was a true gentleman.
fighter
'der Ritter' and 'der Kämpfer' can both mean a person who fights. However, 'der Ritter' belongs above all to the world of the Middle Ages: he is an armored warrior, often on horseback and with a specific social role. 'Der Kämpfer' is much more general. It can be a soldier, a boxer, or a martial artist. When the context is history, castles, and the Middle Ages, 'Ritter' fits. When the only important point is that someone fights, 'Kämpfer' is more natural.

Im Museum sahen wir die schwere Rüstung eines Ritters.
At the museum, we saw the heavy armor of a knight.
Im Ring blieb der Kämpfer ruhig und wartete auf den richtigen Moment.
In the ring, the fighter stayed calm and waited for the right moment.