Is joint tenants in common and tenants in common the same thing?

Joint tenants in common is the wrong way to express a tenancy in common. Some states and legal writers erroneously refer to tenants in common as a form of joint ownership. The better way to refer to the different ways multiple owners can own real property is co-ownership or concurrent ownership because there is a very particular form of co-ownership called a joint tenancy. Tenancy in common and joint tenancy are very different.

You can read about the different forms of co-ownership, including tenants in common, at the related question link.