Add a preamble to the tutorial to introduce domain-specific language

data/tutorials/language/1ms_02_dune.md

@@ -15,6 +15,12 @@ Dune provides several means to arrange modules into libraries. We look at Dune's
 
 This tutorial uses the [Dune](https://dune.build) build tool. Make sure you have version 3.7 or later installed.
 
+In the following toy project, we create an OCaml library for the World Meteorological Organization, with clouds as its subject.
+
+We use unique terms for different elements of our project to avoid ambiguity. For instance, the directory containing the file `cloud.ml` isn't named `cloud`. A different term is used. We also use the Spanish word "nube" and the [Nahuatl](https://en.wikipedia.org/wiki/Nahuatl) word "mixtli," where both terms mean "cloud."
+
+**Note**: The other terms we use are classifications of clouds. These include "[cumulus](https://en.wikipedia.org/wiki/Cumulus_cloud)" (fluffy), "[nimbus](https://en.wiktionary.org/wiki/nimbus)" (precipitating), "[cumulonimbus](https://en.wikipedia.org/wiki/Cumulonimbus_cloud)" (fluffy and precipitating), "[nimbostratus](https://en.wikipedia.org/wiki/Nimbostratus_cloud)" (flat, amorphous and precipitating), and "[altocumulus](https://en.wikipedia.org/wiki/Altocumulus_cloud)" (high altitude and fluffy).
+
 ## Minimum Project Setup
 
 This section details the structure of an almost-minimum Dune project setup. Check [Your First OCaml Program](/docs/your-first-program) for automatic setup using the `dune init proj` command.
@@ -88,7 +94,7 @@ You can also configure your editor or IDE to ignore it too.
 In OCaml, each `.ml` file defines a module. In the `mixtli` project, the file `cloud.ml` defines the `Cloud` module, the file `wmo.ml` defines the `Wmo` module that contains two submodules: `Stratus` and `Cumulus`.
 
 Here are the different names:
-* `mixtli` is the project's name (it means *cloud* in Nahuatl).
+* `mixtli` is the project's name (it means *cloud* in [Nahuatl](https://en.wikipedia.org/wiki/Nahuatl)
 * `cloud.ml` is the OCaml source file's name, referred as `cloud` in the `dune` file.
 * `nube` is the executable command's name (it means *cloud* in Spanish).
 * `Cloud` is the name of the module associated with the file `cloud.ml`.