Some time ago, I asked my brother Massimo, a long time practitioner of Tai chi chuan, what difference there was between this one and Yoga.
After a short pause to thought, he replied:
Tai chi chuan is dynamic, Yoga is static.
Initially I got the reply to the letter, without any more consideration.
After that, recently, I read some note about the topic. And I've noticed some facts.
Tai chi chuan was born as a fighting technique. Yoga as meditation and ascetic practices (see definitions in Wikipedia, which I linked at the top of the article). Their origins are the opposites of each other.
Tai chi chuan has its roots in Chinese philosophies, including the Taoism inheriting from this the concept of alternation of opposites (Yin and Yang). It trains the practitioner to the fundamental principle Wu wei or, consciously, do not act: let things happen.
Yoga is deeply connected to the evolution of Indian philosophy and religion since ancient times, we are speak about two thousand years before Christ. And it aims to bring the practitioner to a total control of its thoughts.
You can see the contact points, albeit from contexts so far? Both leas the learner to rise himself from the world.
I believe that my brother, with his synthetic response, tried to tell me more than I realized at the time.