Kung fu and Tai chi

Kung fu noun - A Chinese martial art.

Tai chi and kung fu are semantically related In some cases you can use "Tai chi" instead a noun phrase "Kung fu".

Tai chi noun - A Chinese system of slow meditative physical exercise designed for relaxation and balance and health.

Kung fu and tai chi are semantically related in far eastern discipline or sport topic. You can use "Kung fu" instead a noun phrase "Tai chi", if it concerns topics such as combat technique.