I think the tags are different. Let me explain with an example:
definitions: What is a deep neural network?
Terminology: Would this (< Insert some tech. behind some AI product/bot >) be a deep neural network or a RNN?
Hmmm I don't feel like they should necessarily be the same. In most machine learning contexts especially, as you say, I would view "evaluation" as something broader or more general than "testing". I guess I'd associate "testing" specifically with the classic train/validation/test data splits.
I could also see testing being used ...
It's telling that it's much easier to create tags than remove them, and I have to wonder if this is intentional or just a fail-safe, to avoid untagged questions.
I like tags in general because they allow degrees of specificity. For instance, most of our questions involve machine learning, but in relation to what?
That said, there is a lot to digest in ...
Done - a tag synonym has been created and conv-neural-network has been merged into convolutional-neural-networks, thereby updating all existing questions. This has the added benefit of making the tag name consistent with all the other pluralized ones.
I think that "deep learning" is already a standard expression, so this tag should be the main tag. The tag deep-network could also exist on this website, given that the expression "deep neural network" is also common, but I would not say that it is a synonym for deep-learning. A deep network is a network that is deep (that is, it possesses "many" layers). ...