A factoid [fak-toid] is a questionable or spurious (unverified, false, or fabricated) statement presented as a fact, but without supporting evidence. The word can also be used to describe a particularly insignificant or novel fact, in the absence of much relevant context. The word is defined as ‘an item of unreliable information that is repeated so often that it becomes accepted as fact.’

The term was coined by Norman Mailer in his 1973 biography of Marilyn Monroe. He described a factoid as ‘facts which have no existence before appearing in a magazine or newspaper,’ and created the word by combining ‘fact’ and the ending -‘oid’ to mean ‘similar but not the same.’ ‘The Washington Times’ described Mailer’s new word as referring to ‘something that looks like a fact, could be a fact, but in fact is not a fact.’

A common factoid states that The Great Wall of China is the only man-made object visible from the moon. In reality no man-made object on Earth can be seen with the naked eye from the Earth’s moon. Given good circumstances one might be able to discern the result of some human activity such as the changing of the Netherlands’ coast or the partial drying out of the Aral Sea, but even that would not be easy. Some astronauts have reported seeing the Great Wall from low earth orbit, among a number of man-made structures. Another factoid states that dogs and cats are color-blind and see the world in scales of grey. That is wrong. They do have color vision, dichromate, but not nearly as good as that of humans, trichromate, i.e., red, green, and blue light.

The word factoid is now sometimes also used to mean a small piece of true but valueless or insignificant information, in contrast to the original definition. This usage was popularized on cable TV by ‘Headline News’ in 1980s and 1990s, which frequently included such a fact under the heading ‘factoid’ during newscasts. ‘BBC Radio 2’ presenter Steve Wright uses factoids extensively on his show. Occasionally these can be incorrect, such as in September 2012 defining a Googol as the number 1 followed by one million zeroes, when the correct definition is the number 1 followed by one hundred zeroes.

As a result of confusion over the meaning of factoid, some English-language style and usage guides recommend against its use. Language expert William Safire in his ‘On Language’ column advocated the use of the word ‘factlet’ to express a ‘little bit of arcana.’