In contemporary Yoga schools you often hear the word ‘Yogi’ being used for anyone who enjoys regularly attending Yoga classes. While actually, for a practitioner of Yoga there is a different word: sādhaka. A sādhaka is someone who performs a sādhana, or Yogic exercise. Such exercises might be aimed at ultimately reaching a state of Yoga, but often don’t lead there yet.
A Yogi is a person who has experienced a state of Yoga or Union with the Divine and seeks to dwell in it whenever he/she/they can. So you could say, such a person is a ‘succesful’ Yoga practitioner. The epithet ‘Yogi’ is therefore more like a landmark on the spiritual path. An indicator that one doesn’t only walk the path, but is also capable of finding one’s way on it.
In our school, therefore, we consider students to be sādhakas and only certain sādhakas to be Yogis.