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Feather fletching – these are shield cut with barred red hen feathers and a solid white cock.
Fins are used by aquatic animals, such as this orca, to generate thrust and control the subsequent motion
Plastic fletching (also known as vanes) – this example is parabolic cut with pink hen vanes (the ones put oblique to the bow when nocked on the string) and a green cock (the one – or ones, with even-numbered vanes – put perpendicular to it).
Caudal fin of a great white shark
Aquatic animals typically use fins for locomotion
(1) pectoral fins (paired), (2) pelvic fins (paired), (3) dorsal fin, (4) adipose fin, (5) anal fin, (6) caudal (tail) fin
Comparison between A) the swimming fin of a lobe-finned fish and B) the walking leg of a tetrapod. Bones considered to correspond with each other have the same color.
In a parallel but independent evolution, the ancient reptile Ichthyosaurus communis developed fins (or flippers) very similar to fish (or dolphins)
In the 1990s the CIA built a robotic catfish called Charlie to test the feasibility of unmanned underwater vehicles

Fletching is the fin-shaped aerodynamic stabilization device attached on arrows, bolts, darts, or javelins, and are typically made from light semi-flexible materials such as feathers or bark.

- Fletching

Stabilising fins are used as fletching on arrows and some darts, and at the rear of some bombs, missiles, rockets, and self-propelled torpedoes.

- Fin
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Traditional target arrow (top) and replica medieval arrow (bottom).

Arrow

Traditional target arrow (top) and replica medieval arrow (bottom).
Modern arrow with plastic fletchings and nock.
Warring States bronze arrowheads
Schematic of an arrow with many parts.
A sideprofile of an Easton Carbon One arrow with a spine of 900, taken with a scanning electron microscope (SEM). The arrow is a bond of two carbon tubes, an inner and an outer tube (black wires). In between both carbon layers, another fiber is used (white fiber). This second fiber is an Mg-Al-Si-fiber. The "white" fiber is twisted around the inner carbon tube. The fibers of the carbon tubes are not twisted, to ensure a maximum of possible mechanical tension of the arrow. The Mg-Al-Si-fiber enhances the flexibility of the arrow. The diameter of a single carbon fiber is approx. 7 µm.
Obsidian broadhead
Ancient Greek bronze arrowhead, 4th century BC, from Olynthus, Chalcidice
Various Japanese arrowheads
Native American arrowheads
20th century field points
Modern replicas of various medieval European arrowheads
Straight parabolic fletchings on an arrow.

An arrow is a fin-stabilized projectile launched by a bow.

A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers called fletchings mounted near the rear, and a slot at the rear end called a nock for engaging the bowstring.