young of domestic cattle
"The farmer gently brushed the newborn calf to help it stand on its wobbly legs."
young of various large placental mammals e.g. whale or giraffe or elephant or buffalo
"The massive gray calf swam alongside its mother in the deep ocean."
A young cow or bull.
"After running up the hill, she felt a sharp cramp in her calf."
The back of the leg below the knee.
In plain English: A calf is either a baby cow or the back part of your lower leg below the knee.
"The baby calf ran alongside its mother after being born."
The word "calf" comes from Old English, where it originally meant a young cow or bull. Its roots trace back to the Proto-Germanic language, though its ultimate origin remains uncertain.