A coffin is a funerary

Funeral

A funeral is a ceremony for celebrating, sanctifying, or remembering the life of a person who has died. Funerary customs comprise the complex of beliefs and practices used by a culture to remember the dead, from interment itself, to various monuments, prayers, and rituals undertaken in their honor...

 box

Box

Box describes a variety of containers and receptacles for permanent use as storage, or for temporary use often for transporting contents. The word derives from the Greek πύξος , "box, boxwood"....

 used in the display and containment of dead people – either for burial

Burial

Burial is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over.-History:...

 or cremation

Cremation

Cremation is the process of reducing bodies to basic chemical compounds such as gasses and bone fragments. This is accomplished through high-temperature burning, vaporization and oxidation....

.

Contemporary North American English

North American English

North American English is the variety of the English language of North America, including that of the United States and Canada. Because of their shared histories and the similarities between the pronunciation, vocabulary and accent of American English and Canadian English, the two spoken languages...

 makes a distinction between "coffin", which is generally understood to denote a funerary box having six sides in plan view, and "casket

Casket

A casket, or jewelry box is a term for a container that is usually larger than a box, and smaller than a chest, and in the past was typically decorated...

", which generally denotes a four-sided (almost always rectangular

Rectangle

In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle...

) box.
First attested in English 1380, the word coffin derives from the Old French

Old French

Old French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...

 cofin, from Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 cophinus, which is the latinisation

Latinisation (literature)

Latinisation is the practice of rendering a non-Latin name in a Latin style. It is commonly met with for historical personal names, with toponyms, or for the standard binomial nomenclature of the life sciences. It goes further than Romanisation, which is the writing of a word in the Latin alphabet...

 of the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 κόφινος (kophinos), "basket".