An iota is something very small. An iota is the smallest letter of the Greek alphabet.

: a white moderately hard and crumbly Greek cheese made from sheep’s or goat’s milk and cured in brine.

The iota subscript is a diacritic mark in the Greek alphabet shaped like a small vertical stroke or miniature iota ⟨ι⟩ placed below the letter. It can occur with the vowel letters eta ⟨η⟩, omega ⟨ω⟩, and alpha ⟨α⟩.

A coalition or union of two vowel sounds pronounced in one syllable; as, ou in out, oi in noise; — called a proper diphthong. A vowel digraph; a union of two vowels in the same syllable, only one of them being sounded; as, ai in rain, eo in people; — called an improper diphthong.

Greek Iota / Ypogegrammeni

Capital “M” is conventionally the widest. I believe the letter W is the widest. Depending on your platform, there might be a way to “getWidth” from a string or DrawText() function somehow with a width property.

Now it’s official, with the Official World Record organisation verifying the 290 metre letter as the longest letter believed to have ever been written.

isoleucine

ηλεκτροεγκεφαλογραφήματος (ilektroenkefalografímatos), 25 letters) meaning “electroencephalogram”. The longest Greek word has 172 letters and 78 syllables. The transliteration has 182 Latin characters. It is the longest word ever to appear in literature according to the Guinness World Records (1990).

The longest word of classical Latin is the word subductisupercilicarptor [24 characters], meaning “a person who criticizes and raises his eyebrows upwards” – literally, this term was for extremely critical critic.