In English, the word for "arm" is "arm". You can use it to refer to the body part that extends from the shoulder to the hand, or you can use it more generally to mean a limb or appendage on a living organism. For example, you can say "I have a pain in my arm" to refer to your body's arm, or you could say "the octopus has eight arms" to refer to the octopus's limbs.
