I do yôga means practically nothing. Saying that one practices yoga is analogous to declaring that one plays sports.

Two people meet and one declares I come from doing sports to which the other replies what a coincidence, I also come from doing sports. This brief conversation could leave the impression that both are engaged in the same activity. However, we know that this is not necessarily the case. One can play rugby and the other golf. If we broaden the idea of sport, it could even be that one goes running and the other plays chess, or plays some e-sport.

We realize then that saying I play sports does not define precisely what it is that they do. It is not that the statement is incorrect but it is clear that in most contexts we will need more precision.

Among sports we have soccer, tennis, golf, volleyball, ping-pong. All are played with a ball. They are all sports; but we would never say that they are the same, or even that they are similar.

Those two people conversing may both play sports, but it is quite possible that they do not enjoy each other's sports.

On the other hand, although we must agree that talking about sport is vague and not at all precise, the word still defines something. There are characteristics that make an activity a sport or not. If someone says they are doing sport we will never imagine that they are sleeping, watching a movie or eating.

So let's go back to yoga.

Yôga is not sport, it is philosophy, but like the word sport, the word yôga does not define an activity per se, but a type of activity. An activity with a very specific purpose.

Not just any activity is yôga, but no two types of yôga are the same. So diverse are the types of activities that can be classified as yôga (traditionally 108) that in effect what has happened in the last few decades is that the word has completely lost meaning. No one knows what it is and so anything can be it.