Secondly: Difference between `Arafah and `Arafat
Some hold that `Arafah and `Arafat are synonymous: they are both proper names for the place where one stands, and names for the well-known place where standing is wajib. Others hold that only `Arafat is the name of the hill or well-known place. As for `Arafah, it is not a name of the place, but of the day one stands at `Arafat.
As for the word `Arafat, it is a name that takes the form of a plural, so it cannot be pluralized. Some hold that `Arafat is the plural of `Arafah, as though every plot of land there is `Arafah and so the combination of them was named `Arafat. Others hold that the name is plural while the named object is singular.

Thirdly: Merits of the day of `Arafah
1. Allah frees His slaves from the Fire on this day more than any other
2. On this day, Allah revealed His Word: “Today I have perfected your religion for you, and I have completed My favour upon you, and I have approved Islam for you as religion.” (Al-Ma’idah: 3)
3. Fasting the Day of `Arafah expiates for the sins of the previous and coming years
4. The best of actions are those during the first ten days of Dhu al-Hijjah. The Day of `Arafah is the ninth day of these ten, so it also has this merit.