This chapter introduces language invention. It addresses the similarities and differences between natural languages (natlangs) and constructed languages (conlangs) and distinguishes the latter from creative language forms such as slang and language games. This chapter also covers the main types of conlangs and the key motivations underlying language invention. It also discusses important considerations to keep in mind when creating a language and provides a guided exercise on language invention. The chapter ends with a list of resources and references to explore further.

Esperanto was created in the nineteenth century by the Warsaw-based ophthalmologist L. L. Zamenhof (1859–1917) as a universal second language; he called it Lingvo Internacia, the international language, hoping that it would foster global peace and understanding. Esperanto isn’t the only constructed language, but it is the most popular; it is also the one with the richest cultural legacy and a complex history of dictionaries. Offering a comparative analysis of the dictionary tradition of Esperanto, this conversation compares that tradition to other languages. Ludovik Zamenhof is discussed as the seminal figure in that tradition. It looks at translation as a force changing Esperanto, reflects on the tension between particularism and universalism, and questions Esperanto’s Eurocentrism. It meditates on how the internet has changed Esperanto lexicography. Finally, it explores canonical lexicons such as the Baza Radikaro Oficiala, published under the aegis of the Academy of Esperanto, as well as the Plena Vortaro de Esperanto, released by the Sennacieca Asocio Tutmonda, as well as Kazimierz Bein’s Vortaro de Esperanto, and the Plena Ilustrita Vortaro.

We have seen that in normal cases children create their mental grammar from input that has been called “poor,” but that language fails to emerge when input is totally absent. Chapter 12 shows that when the input is of “extra-poor” quality, children nevertheless manage to arrive at mental grammars of apparently sufficient complexity. The relevant situation can lead to the emergence of whole new languages. The key claim is that children, when exposed to a so-called pidgin (a relatively primitive system of communication created by adults who do not share a common language), transform such an impoverished language into a full-fledged language, which we call a creole. How can children do this? Nativists have argued that children can do this because they have an innate “manual” that dictates the construction of a mental grammar, no matter how impoverished the input. This leads to the creolization argument in support of the Innateness Hypothesis. This chapter also surveys various kinds of artificially constructed languages that are typically created by adults who either want to design a universal language or to provide groups of people in fictional stories with their own language.

This chapter is about the words in planned and constructed languages.

This last chapter deals with three remaining issues, each with a dedicated section: macro families, sign languages, and constructed languages. Several major proposals that combine well-established language families into larger macro families are outlined, including the famous Nostratic hypothesis, as well as some lesser-known hypotheses such as the Dene-Yeniseian and Ural-Altaic hypotheses. The second section discusses sign languages and argues that they are like oral languages in that they have grammatical patterns of their own. The final section gives a brief overview of artificially constructed languages and how they differ from natural human languages, to which the majority of this book is dedicated.