What are the longest words in the French language?

If you bring up the ‘longest word’ debate with a group of French people, anticonstitutionnellement will most likely be cited as the winning entry. 

However, while boasting an impressive 25 letters, this word is not actually the longest in the French dictionary.

We look at the meaning of some of the most lengthy French words so you can impress native speakers with your tongue-twisting vocabulary.

Read also: Master French pronunciation with classic tongue twisters

Anticonstitutionnellement (25 letters)

Translation: unconstitutionally. 

It describes doing something in a way that contradicts the fundamental principles or laws of a constitution.

Many French people grew up learning that anticonstitutionnellement is the longest ‘commonly-used’ word in the dictionary. 

Intergouvernementalisations (27 letters) 

Translation: intergovernmentalisations. 

It refers to a political process whereby several governments work together to implement common policies.

A social media rumour suggested that this 27-letter word has taken the top spot from anticonstitutionnellement.

The claim has not however been confirmed by the Académie française (the responsible council for matters concerning the French language). 

This discussion also led to disagreements as to whether plurals should be taken into consideration. 

Heptathalassoédimbourgeoises (28 letters)

This geographical word describes the residents of Édimbourg-des-Sept-Mers (Edinburgh of the Seven Seas), which is the capital of the British volcanic island, Tristan da Cunha.

One of the longest town names in France is Saint-Remy-en-Bouzemont-Saint-Genest-et-Isson (38 letters), located in the north-east of the country, however the locals are simply referred to as les Bouzemontois. 

Supercalifragilisticexpidélilicieux (35 letters)

Translation: supercalifragilisticexpialidocious. 

It describes something extraordinarily good. This word is not officially included in the French dictionary however it has become a well-known reference due to the classic film, Mary Poppins. 

It is worth noting that some versions in France maintain the original word while others transition into a délilicieux (delilicious) ending.

For a French literary alternative we can look to Candide by Voltaire, where the character Pangloss invents the term métaphysico-théologo-cosmolo-nigologie (35 letters) in reference to fantasy science. 

Read also: Understanding 'un gros mot': French swear words and their cultural significance

Hippopotomonstrosesquipédaliophobique (37 letters)

Translation: hippopotomonstrosesquippedaliophobic. 

It ironically refers to a person who is afraid of long words.

To break it down: the first section stems from hippopotame (hippopotamus), followed by the Latin monstrŭōsus (meaning monstrous or extraordinary), then sesquipédal (referring to a word with many syllables) and finally, phobie (describing a fear of something).

Similarly, hexakosioihexekontahexaphobie (29 letters) is the fear of the number 666, which can sometimes be considered a bad omen.

Aminométhylpyrimidinylhydroxyéthylméthythiazolium (49 letters)

Extending the discussion to include medical or scientific vocabulary reveals lots more long and technical terms. This particular example comes from chemistry, referring to a molecule for the B1 vitamin. 

The scientific name for titin, the longest known protein in the human body, begins methionyl... and ends ...isoleucine, and contains several tens of thousands of other letters in between. 

Some argue it could be the longest word in any language, however, lexicographers technically reject names of chemical compounds from official word lists. 

Read also: Discover the latest words in the new Académie Française dictionary edition