People sometimes muddle-up tai chi and yoga.
It is common to see yoga postures labelled "tai chi" on Pinterest, Facebook etc.
Such confusion is only possible when a person has studied neither yoga nor tai chi chuan, for the arts are very different indeed.
Yoga is about stretching, balancing and physical unity. Tai chi chuan is a style of kung fu; a martial art.
The differences significantly outweigh any superficial similarities.