What is meant by "the forearm" regarding a woman's nakedness in front of another woman, and does it include both the forearm and the upper arm?

The majority of scholars hold that the 'awrah (area of modesty) of a Muslim woman in front of another Muslim woman is the area between the navel and the knee. This is the preponderant opinion. Based on this, a woman's entire arm, including the upper arm, is not considered 'awrah in front of another Muslim woman. There are other opinions among the people of knowledge regarding this issue. As for the 'awrah of a Muslim woman in front of a non-Muslim woman, there is a difference of opinion among the jurists.