The traditional GI top is called uwagi and the traditional pants are called zuban and the belt is called the obi. Some schools also train in the hakama (split skirt pants). 
There is no such word as "gi"; without a preceding syllable, the character would have to be read as "ki", as in "kimono". 
Obi - belts
To wash or not to wash
On 'washing away the training, knowledge and experience'
There is the myth that in ancient days a student of the martial arts would start training wearing a white belt. Over time and through practice that white got darker due to sweat, blood and tears (and those dirty hands of yours). Eventually that white belt would have turned black. So that (dirty) black symbolizes your knowledge gained through practice.
Unfortunately this myth is just that - a myth. Kano (founder of Judo?
) introduced colored belts and their representation of ranking into the martial arts. Nothing old. Just 100 years. No dirty black belt. Just dyed.
You don't wash away your knowledge and experience by washing your belt. Just bacteria. Thanks!
At the British Aikido Federation Summer school last year one of the Japanese Guest Sensei (Fujita Sensei) explained he felt that the correct way to tie one's belt involved it being crossed at the back, he also explained that the neater way was considered 'feminine' ??