Alfine – The top-tier groupset in Shimano’s “Pavement” line of cycling components.  The Alfine-11 is an 11-speed internally geared hub in that groupset.

Chain Wrap – Difference between the maximum and minimum front chainring teeth plus the difference between the maximum and minimum rear cog teeth.  Used to determine the amount of chain slack the derailleur arm or tensioner must handle.  Chain wrap of a drivetrain should be less than or equal to the Chain Wrap Capacity specified for the rear derailleur.

Chainline – Distance between the chain and center of the frame.  A drivetrain with single front chain ring and single rear sprocket is considered “perfect” because the the chain line doesn’t change when gears are changed.  More from Sheldon Brown.

Cruciform – The center frame section of a tadpole trike, containing the typical “flying cross” arrangement of a longitudinal tube crossed with a tube connecting the front wheels.

Delta – A recumbent trike configuration with two wheels in the rear and one in front.

Development – Distance traveled per one revolution of the crank, in meters.   Used the same way as Gear Inches.

Di2 – A Shimano electronic shift technology.

Gear Inches – A way to compare between gears the relative distance traveled in one revolution of the crank.  Diameter of the drive wheel * number of teeth in front chainring / number of teeth in rear cog. 

Gear Ratio – Number of teeth in the front chainring divided by the number of teeth in the rear cog.  Some IGH manufacturers define the design limits of the hub in terms of Gear Ratio.  Not a proper definition for the term but the one Shimano uses in their documentation.

HDQ – What I call my current trike which started out as an ICE Q and was recently modified with an ICE Adventure Heavy Duty (HD) cruciform.

ICE – Inspired Cycle Engineering, manufacturer of the Sprint, Adventure, and VTX trikes.

IGH – Internally Geared Hub.  A hub that uses internal, planetary gearing instead of conventional external cogs/derailleurs.  Can be built into the drive wheel, crank, or used in a mid-drive.

Tadpole – A recumbent trike configuration with two wheels in front and one in rear.