This is the 6536th most frequent Russian word.
cамбо
Sambo: A Russian martial art and self-defense system meaning "self-defense without weapons."
Here, 'самбо' refers to the martial art, a proper noun used as a subject in the sentence.
Самбо — это вид спортивного единоборства, разработанный в СССР.
Sambo is a type of martial art developed in the USSR.
In this sentence, 'самбо' refers to the practice or activity of engaging in the martial art.
Он занимается самбо уже пять лет и достиг мастерского уровня.
He has been practicing sambo for five years and has achieved a master level.
Here, 'самбо' indicates the sport associated with competitions and events.