Interlingue

Interlingue — called Occidental until the 1949 rename — is a naturalistic international auxiliary language published in 1922 by Edgar de Wahl, a Baltic German naval officer and teacher living in Tallinn. Where Esperanto builds words from a schematic affix kit, Interlingue takes its vocabulary largely ready-made from the Romance languages and international scientific Latin, so that a reader of French, Spanish or English can often follow a text at sight. Its signature invention is de Wahl's rule, a regular procedure for deriving nouns and adjectives from verb infinitives that reproduces the Latin double-stem alternations (vider 'to see' → vision) without listing them as exceptions. The language flourished in the 1930s and 1940s around the magazine Cosmoglotta, published from Vienna and then Switzerland, but collapsed after the rival Interlingua appeared in 1951 and de Wahl died in Soviet-occupied Tallinn. A small community revived it online from the 2000s; it has no native speakers, an active Wikipedia and a handful of open dictionaries.