Achilles and Achilles tendon

Achilles noun - A mythical Greek hero of the Iliad; a foremost Greek warrior at the siege of Troy; when he was a baby his mother tried to make him immortal by bathing him in a magical river but the heel by which she held him remained vulnerable--his `Achilles' heel'.

Achilles tendon and Achilles are semantically related. In some cases you can use "Achilles tendon" instead a noun "Achilles".

Achilles tendon noun - A large tendon that runs from the heel to the calf.

Achilles and Achilles tendon are semantically related. You can use "Achilles" instead a noun phrase "Achilles tendon".