How many dimensions?

A grid has only one dimesnion.
A block can have 3 dimensions. (Some say 2 dim.)
A thread can have ? dimensions. (Some say 2, others say 3.)

I’m finding conflicting info.
Please correct my info.

Thanks

Your terminology isn’t quite right.

A grid is a 1 or 2 dimensional array of blocks (sometimes called “thread blocks” in the documentation). A block is a 1, 2, or 3 dimensional array of threads. Threads are the smallest unit of execution and have no dimensions.

The CUDA Programming Guide (Section 2.2 and Appendix G) is the authoritative reference here.

A grid has 2 dimensions (but with CUDA 4 on fermi you can have 3 dimensions). It consists of blocks.
A block has 3 dimensions. It consists of threads.