Penny-farthing frames are characterized by a large front wheel and a small rear wheel.
The cycle types article describes additional variations.
In a compact-geometry frame, the top tube is normally sloped downward toward the seat tube for additional standover clearance.
In a mountain bike frame, the top tube is almost always sloped downward toward the seat tube.
A cross frame consists mainly of two tubes that form a cross: a seat tube from the bottom bracket to the saddle, and a backbone from the head tube to the rear hub.
Folding bicycle frames are characterized by the ability to fold into a compact shape for transportation or storage.
Radically sloped top tubes that compromise the integrity of the traditional diamond frame may require additional gusseting tubes, alternative frame construction, or different materials for equivalent strength.
(See Road and triathlon bicycles for more information on geometries.) Step-through frames usually have a top tube that slopes down steeply to allow the rider to mount and dismount the bicycle more easily.
The main triangle consists of the head tube, top tube, down tube and seat tube.
The rear triangle consists of the seat tube, and paired chain stays and seat stays.
In the diamond frame, the main "triangle" is not actually a triangle because it consists of four tubes: the head tube, top tube, down tube and seat tube.
The rear triangle consists of the seat tube joined by paired chain stays and seat stays.
A frameset consists of the frame and front fork of a bicycle and sometimes includes the headset and seat post.