It is a topknot. The chonmage is the topknot worn for daily ware. The highest ranking Yokozuna wear the gingko leaf.
The hair style depends on the rank of the sumo. The lowest ranks have no knot. Conmage topknot is for the makushita. The highest ranks wear it in a style known as the ginko leaf.
It is called a comb.
It is called a topknot.
In Japanese, there is no visible indication, it is determined by the context. He was a sumo wrestler. There were ten sumo in that stable.
Sumo wrestlers live in Japan in stalls with other Sumo and their masters.
Sumo is a type of wrestling from Japan. Sumo wrestlers are usually strong and fat.
Sumo is a Japanese sport. There are Chinese sumo wrestlers.
What English-speakers think of when they say "sumo" (i.e. heavyset men wrestling) is also called "sumo" in Japanese. Basically, sumo is sumo!