die Ferse
heel
The rear, lower part of the human foot below the ankle.
Nach der langen Wanderung schmerzte ihm die Ferse.
After the long hike, his heel hurt.

heel
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heel
The rear, lower part of the human foot below the ankle.
Nach der langen Wanderung schmerzte ihm die Ferse.
After the long hike, his heel hurt.

The expression 'die Achillesferse' (Achilles' heel) is derived from 'Ferse' (heel) and refers to the only vulnerable spot of a person or system. It comes from Greek mythology and is very common in German.
Seine Unpünktlichkeit ist seine Achillesferse im Berufsleben.
His unpunctuality is his Achilles' heel in his professional life.
In the literal sense, 'Ferse' (heel) is often associated with pain or injuries. You can 'sich die Ferse stoßen' (bump your heel) or 'Schmerzen in der Ferse haben' (have pain in your heel).
Ich habe mir beim Sport die Ferse verletzt.
I injured my heel while playing sports.
The idiom 'jemandem auf den Fersen sein' (to be on someone's heels) is a fixed construction. The person being pursued is always in the dative case.
Die Konkurrenz ist uns dicht auf den Fersen.
The competition is close on our heels.
heel / paragraph / sales
'der Absatz' and 'die Ferse' are in a similar area, but they do not belong to the same thing. 'die Ferse' is part of the foot, so it is a body part. 'der Absatz' is part of the shoe, namely the raised part at the back under the heel. The words can be confusing because the heel of the shoe sits directly under the heel of the foot. When it is about the foot, 'Ferse' fits. When it is about the shoe, 'Absatz' fits.

Nach dem langen Spaziergang tut mir die Ferse weh.
After the long walk, my heel hurts.
Der Absatz ihrer neuen Schuhe ist höher als erwartet.
The heel of her new shoes is higher than expected.