Here’s my take on what to call the different lumber grading by end grain configuration. In my opinion, I say let the wood and the geometry provide the answer: “Radial” is a word taken from the ancient Greek word for “ray”, which is also the source word for radius. Rift and riven are from northern European languages (Norse most likely) meaning “to split.” Logs split naturally radially. The “quarter” in quarter sawn is from quadra, quadrant–which is where quarter-sawn planks are taken as shown. The planks cut out to the left hand side of the log as illustrated here would be called “tangential” because that’s just what they are to circular growth rings.
This terminology is not standardized unfortunately, though I have no idea why not. I think we should let the lumber speak for itself.