Terminology: Is there a technical term for the paired wheels on tricycles?
I have been in the recumbent business for over 10 years and have not ever heard a technical term to distinguish the pair of wheels versus the single wheel. As there is so little standardization it would be difficult to describe the wheels without ever running into someone misunderstanding. I used to manufacture front wheel drive two wheeled recumbents and already got into problems since 'my' front wheels were really rear wheels (135mm hub spacing) and 'my' rear wheels were actually front wheels (100mm hub spacing). Then I started to experiment with trikes where I used a delta setup with a single powered wheel on the front (still 'my' front wheel that was still actually a rear wheel) and two single-sided hub wheels. 

Whenever I had wheels made I found it best to describe as much detail as possible (and still sometimes got reversed quantities) and I did the same in my shop.