From the Greek word κύκλος (kuklos), a circle, a wheel, English derives several means of transportation.  From swiftest to slowest, there are motorcycles, bicycles, tricycles, and unicycles.

The motorcycle is a self powered two-wheeled vehicle.   The first part of the word, motor, comes from the Latin verb moveo (I move.)

The bicycle is a human powered two-wheeled vehicle.  It also happens to be my all time favorite means of transportation.  Once I am done buying music lessons for my kids, I am buying this:

Since my youngest is 8, I will be… well, older than I am now. 

Bicycles need kick stands.  They cannot stand alone as they are two tired.

Bicycle is a combination of the Latin prefix bi (twice) and κύκλος

The tricycle competes with the unicycle for the slowest reputation.  The tricycle is the primary weekend means of transportation among pre-schoolers.  The word comes from Latin tres (three) and κύκλος.

Finally, there is the unicycle.  The unicycle is a one wheeled wonder.  I simply cannot believe that people can ride these things. 

I am truly afraid of unicycles, as I believe they have only one wheel for sinister reasons.  One wheel to rule them all, One wheel to find them, One wheel to bring them all and in the darkness bind them.