
der Felsen
rock
A large, massive rock formation that protrudes from its surroundings, for example on a coast or in the mountains.
Die Wellen brachen an den schroffen Felsen der Küste.
The waves broke against the rugged rocks of the coast.
rock
Loading your saved state.

rock
A large, massive rock formation that protrudes from its surroundings, for example on a coast or in the mountains.
Die Wellen brachen an den schroffen Felsen der Küste.
The waves broke against the rugged rocks of the coast.

a rock in the storm
A person who is very calm, strong, and reliable in difficult or turbulent times and gives others support.
In der Krise war unsere Chefin für das ganze Team ein Fels in der Brandung.
During the crisis, our boss was a rock in the storm for the whole team.
This word belongs to the N-declension. This means that the nominative singular is 'der Fels' (the rock), but in all other cases (genitive, dative, accusative singular and throughout the plural), the form 'Felsen' is used.
Ein großer Fels blockierte den Weg.
A large rock blocked the path.
In its literal meaning, 'Felsen' (rock/rocks) is often combined with adjectives such as 'schroff' (rugged), 'steil' (steep), or 'massiv' (massive). Typical actions are 'auf einen Felsen klettern' (to climb onto a rock) or 'an einem Felsen stehen' (to stand by/on a rock).
Die Bergsteiger kletterten den steilen Felsen hinauf.
The mountain climbers climbed up the steep rock.
The idiom 'ein Fels in der Brandung sein' (to be a rock in the storm/surf) is a fixed expression. It is always used together with the verb 'sein' (to be) to describe a person who is very reliable and calm.
Während des ganzen Projekts war er unser Fels in der Brandung.
Throughout the whole project, he was our rock in the storm.
rock
Fels and Felsen can both refer to solid rock, although Felsen often means a single, prominent formation. However, the fixed expression for a strong and reliable person is “ein Fels in der Brandung” (a rock in the storm). In that expression, Fels cannot be replaced by Felsen.

Ein hoher Felsen ragt an der Küste weit aus dem Wasser.
A tall rock formation juts far out of the water along the coast.
In dieser schweren Zeit ist meine Schwester für mich ein Fels in der Brandung.
During this difficult time, my sister is a rock in the storm for me.