Some people get pretty worked up about using the right word for the right joint. Perhaps they have a point since imprecise use of terms can lead to confusion. So, to be precise, here are the proper definitions:
- A dado is a U-shaped, square-bottomed channel cut across the grain.
- A groove looks just like a dado, but runs with the grain. A lot of people call a groove a dado I think that’s OK – but imprecise.
- A rabbet is an L-shaped channel cut across or with the grain. A rabbet is always cut on the stock’s edge.