One of the cool thing about reading from a Kindle is that it is tied to a dictionary. If you run across a word you don't know you can click on it to reveal the meaning. It would be cool if Logos had such a feature.
This is available in the Information Tool - and in its settings you can determine whether it updates on hover or click
In addition to what Graham shared: even plain English text in not-tagged resources allow dictionary lookup with a double-click, which will invoke the lookup feature (e.g. in Merriam-Webster or the Concise Oxford Dictionary or whatever you have installed for the language your resource is in).
Thanks! thanks is helpful.