The longest word starting with E in a major English dictionary is electroencephalographically, a 27 letter word that means "by means of an electroencephalograph," the machine used to record electrical activity in the brain. It's the second longest entry in the Collins English Dictionary overall, beaten only by dichlorodiphenyltrichloroethane, the chemical name for DDT.

That should settle the question, except that if you search this yourself, you'll find at least three or four different words claimed as the answer, several of them wrong, and almost nobody explaining where their number actually comes from.

Why so many pages disagree

Type this question into Google and you'll get "electroencephalographic" from one site, "electroencephalography" from another, and the full "electroencephalographically" from a third, often with no indication that these are three different words with three different letter counts. The shortest of the group, electroencephalographic, is an adjective at 24 letters. Electroencephalography, the noun for the brain scan itself, is 22 letters. Only the adverb form, electroencephalographically, reaches the full 27.

Most pages just pick whichever version they found first and present it as settled fact. A couple of kids' vocabulary sites even round it off with a vague, feel good definition instead of citing an actual dictionary, which is how you end up with three "correct" answers floating around for the same basic word family.

How a word gets this long

The length isn't random. Electroencephalographically is built from real, meaningful pieces stacked together: electro (relating to electricity), encephalo (relating to the brain), graphy (the process of recording something), and ically (turning it into an adverb). Take any one piece away and you get a shorter, still valid word, which is exactly why the dictionary contains electroencephalogram, electroencephalography, and electroencephalographic as separate entries at different lengths. The 27 letter version is simply the longest branch of that same word family, not a separate invention.

This is common with the longest words in English generally. Almost none of them are long for the sake of being long. They're medical or scientific terms where each prefix and suffix is doing real work, and English lets you chain as many of them together as the concept requires.

If you want a word you might actually use

Electroencephalographically is real, but nobody says it in conversation. If you want something from the same family that you're more likely to actually encounter, electroencephalography is the one that shows up in medical articles, hospital paperwork, and news coverage of sleep studies or seizure diagnosis. It's five letters shorter and still an accurate, dictionary standard word rather than a technicality.

What this means if you're playing a word game

None of this matters if you're stuck on a Scrabble or Words With Friends board, because neither game will let you play a word anywhere close to 27 letters. The Official Scrabble Dictionary lists 7,032 words starting with E, and they range from two letters all the way up to a 15 letter maximum, which is the longest word either game physically allows. Electromyograph, a real 15 letter word for the machine that records muscle activity, is one of the higher scoring options in that range at 28 points before any board bonuses, and embezzlements tops the list of highest scoring E words overall at 37 points.

So if you searched this question because you're actually holding tiles right now, the word you want isn't the dictionary record holder at all. It's whatever fits your rack. WordsGallery's word finder can filter every valid E word by exact length, which is a faster way to find a playable option than trying to remember one from a trivia list.