What is the “When is a Door Not a Door?” Riddle

By Staff WriterLast Updated May 27, 2020 7:44:17 PM ET

When is a door not a door? The simple answer is “When it is ajar.” 

The riddle may seem straightforward, but it has a few complex details worth exploring.

About Ajar

“Ajar,” which the Collins English Dictionary defines as “partly open,” may seem like a pretty straightforward word. However, its etymology is more complex

The Oxford University Press explains that the word “ajar” derives from “on char.” “Char” is related to the Old English word “cierran,” meaning “to turn.” However, this definition is now considered obsolete.

The modern usage of “ajar” first appeared in 1786. However, it did not make its way into a dictionary until 1864, when C.A. F. Mahn updated Webster’s etymology and described ajar as a + jar. He stated that “jar” was a Dutch word meaning “a harsh sound.” He also asserted that the word’s two accepted definitions, “a harsh sound” and “partly open,” were linked due to Shakespeare’s usage of “jar,” “a vibration of the pendulum of a clock.”

However, Oxford University Press found that the second definition of “jar” — “to turn” — is closer to how we use the word ajar today. 

Puns and Wordplay 

The “Door is Not a Door” riddle is an example of wordplay. Also called a pun, wordplay is typically used in books and everyday conversation to elicit humor.

The Oxford Royale Academy says the foundation of puns and wordplay are homophones. Homophones are words that sound the same but are possibly spelled differently and have differing definitions. 

Puns can be jokes. When they are not, we often note that there is “no pun intended.”

Many jokes involve puns and wordplay. Here are some common examples from Literary Devices

  • Time flies like an arrow. Fruit flies like a banana.
  • The life of a patient of hypertension is always at steak.
  • A horse is a very stable animal.

History Behind Doors

Doors have a storied history that goes back thousands of years. While who exactly created the first door is unclear, historical accounts credit Heron of Alexandria with creating the first automatic door.

A mathematician and engineer, Heron lived between 10 CE and 70 CE in Alexandria, Egypt. The University of St. Andrews says he created an automatic temple door opener that was powered by heat and pneumatics.

Heron is known as the great-grandfather of engineering. He also created a wind-powered organ, the first vending machine, and a steam-powered engine.

Other Door Riddles

The “door is not a door” riddle is not the only door-related brain teaser out there. In fact, there are many riddles that involve doors.

Here are some from Riddles and Answers

  • What has no hands but might knock on your door, and if it does you better open up? Opportunity
  • I go through a door but never go in, and never come out. What am I? A keyhole
  • What never asks questions but is always answered? A doorbell
  • What takes many knocks but never cries? A door