Can you name a common four letter word which reads the same upside down as right-side up?

This clever word puzzle relies on the specific geometry of its capital letters. The letter 'O' is naturally symmetrical and appears unchanged when rotated 180 degrees. The true key, however, is the letter 'N'. When capitalized, an 'N' also looks identical after being flipped completely upside down. By combining these rotationally symmetric letters to form the word for midday, you create a perfect visual illusion where the word reads the same from either orientation.

This type of word is a specific example of an ambigram, which is a word or artistic design that can be read in more than one way. More specifically, this is a rotational ambigram. While not extremely common in English, other examples exist, such as "SWIMS" and the international distress signal "SOS," which also retain their meaning when viewed upside down. These visual curiosities are a favorite of graphic designers and typographers who enjoy the challenge of creating symmetrical text.

Ambigrams are often considered the visual cousins of palindromes—words or phrases that read the same forwards and backwards, like "level" or "racecar." Both of these wordplay types rely on a form of symmetry, but one is based on the sequence of letters, while the other is based on the physical shapes of the letters themselves.