"Dord" is the only nonexistent word ever mistakenly added to a Merriam-Webster publication. The fictitious term was listed in their New International Dictionary from 1934 to 1947. The mistake began with a short note turned in by a chemistry consultant in 1931, intending to add the word "density" to the list of words that were abbreviated with the letter ‘D’. The card read in its entirety: "D or d, cont. Physics & Chem. density." When terms were being defined, spaces were added between each letter to leave room for possible marks showing stress and syllable breaks. The reviewing editor assumed a space had been missed between the ‘o’ and ‘r’ and marked the entire "D or d" as a single word, defined as "density". Though words went through several levels of checks in the process of being defined, all missed the mistake. A simple pronunciation was penned, but no etymology was added. It made it into the final published version as "dord (dôrd), n. Physics & Chem. Density”. In 1939, an editor noticed the word lacked an etymology, investigated, and put out a correction slip marked “IMPERATIVE! URGENT! A ghost word!" Even then, the entry remained in the dictionary for eight more years. Dord remains the one and only "ghost word" ever to make it into a Merriam-Webster dictionary.