diff --git a/docs/source/_ext/entities.py b/docs/source/_ext/entities.py
new file mode 100644
index 00000000..3ec47773
--- /dev/null
+++ b/docs/source/_ext/entities.py
@@ -0,0 +1,251 @@
+from collections import defaultdict, abc
+from typing import cast
+
+from docutils import nodes
+from docutils.parsers.rst import Directive
+
+import sphinx
+from sphinx.locale import _
+from sphinx.util.docutils import SphinxDirective
+from sphinx.errors import ExtensionError
+
+from conf import languages as LANGUAGES
+
+logger = sphinx.util.logging.getLogger(__name__)
+
+GLOBALNAME = "$GLOBAL$"
+
+
+def update(d, u):
+    for k, v in u.items():
+        if isinstance(v, abc.Mapping):
+            d[k] = update(d.get(k, {}), v)
+        else:
+            d[k] = v
+    return d
+
+
+class EntityNode(nodes.General, nodes.Element):
+    pass
+
+
+class EntitiesNode(nodes.General, nodes.Element):
+    pass
+
+
+class AllEntities:
+    def __init__(self):
+        self.entities = defaultdict(dict)
+
+    @classmethod
+    def install(cls, env):
+        if not hasattr(env, "entity_all_entities"):
+            entities = cls()
+            env.entity_all_entities = entities
+        return env.entity_all_entities
+
+    def merge(self, other):
+        self.entities.update(other.entities)
+
+    def purge(self, docname):
+        for env_docname in [GLOBALNAME, docname]:
+            self.entities[env_docname] = dict(
+                [
+                    (name, entity)
+                    for name, entity in self.entities[env_docname].items()
+                    if entity["docname"] != docname
+                ]
+            )
+
+    def _extract_entities(self, nodes):
+        pass
+
+    def _extract_options(self, nodes):
+        pass
+
+    def _add_entities(self, entities, language, is_global, docname):
+        scope = GLOBALNAME if is_global else docname
+        for entity in entities:
+            name = f'{language}-{entity["name"]}'
+            content = entity["content"]
+
+            if name in self.entities[scope]:
+                logger.warning(
+                    f'Entity "{name}" has already been defined{" globally" if is_global else ""}',
+                    location=docname,
+                )
+
+            self.entities[scope][name] = {"docname": docname, "content": content}
+
+    def _extract_global(self, nodes):
+        for node in nodes:
+            if node.tagname != "field":
+                raise Exception(f"Expected a field, found {node.tagname}")
+
+            name, _ = node.children
+            if name.tagname != "field_name":
+                raise Exception(f"Expected a field name here, found {name_node.tagname}")
+
+            if str(name.children[0]) == "global":
+                return True
+
+    def _extract_entities(self, nodes):
+        entities = []
+        for node in nodes:
+            if node.tagname != "definition_list_item":
+                raise Exception(f"Expected a list item here, found {node.tagname}")
+
+            name_node, content_node = node.children
+            if name_node.tagname != "term":
+                raise Exception(f"Expected a term here, found {name_node.tagname}")
+            if content_node.tagname != "definition":
+                raise Exception(f"Expected a definition here, found {content_node.tagname}")
+            if content_node.children[0].tagname != "paragraph":
+                raise Exception(
+                    f"Expected a paragraph here, found {content_node.children[0].tagname}"
+                )
+
+            name = str(name_node.children[0])
+            content = content_node.children[0].children[0]
+            entities.append({"name": name, "content": content})
+        return entities
+
+    def extract(self, node, docname):
+        is_global = False
+        entities = []
+
+        language = None
+        for node in node.children:
+            if language is None and node.tagname != "paragraph":
+                raise Exception(f"Expected language name:\n.. entities:: <LANGUAGE>")
+            elif language is None and node.tagname == "paragraph":
+                language = str(node.children[0])
+                if language not in LANGUAGES:
+                    raise Exception(
+                        f'Unknown language "{language}. Might be missing a newline after language"'
+                    )
+            elif node.tagname == "field_list":
+                is_global = self._extract_global(node.children)
+            elif node.tagname == "definition_list":
+                entities.extend(self._extract_entities(node.children))
+            else:
+                raise Exception(f"Expected a list of terms/options, found {node.tagname}")
+
+        self._add_entities(entities, language, is_global, docname)
+
+    def resolve_pendings(self, app):
+        env = app.builder.env
+
+        updates = defaultdict(dict)
+        for env_docname in self.entities.keys():
+            for name, entity in self.entities[env_docname].items():
+                docname = entity["docname"]
+                node = entity["content"]
+
+                if node.tagname == "pending_xref":
+                    contnode = cast(nodes.TextElement, node[0].deepcopy())
+                    newnode = None
+
+                    typ = node["reftype"]
+                    target = node["reftarget"]
+                    refdoc = node.get("refdoc", docname)
+                    domain = None
+
+                    try:
+                        if "refdomain" in node and node["refdomain"]:
+                            # let the domain try to resolve the reference
+                            try:
+                                domain = env.domains[node["refdomain"]]
+                            except KeyError as exc:
+                                raise NoUri(target, typ) from exc
+                            newnode = domain.resolve_xref(
+                                env, refdoc, app.builder, typ, target, node, contnode
+                            )
+
+                        if newnode is None:
+                            logger.warning(f"Can't resolve node: {node}")
+                    except NoUri:
+                        newnode = contnode
+
+                    updates[env_docname][name] = {"docname": docname, "content": newnode}
+
+        update(self.entities, updates)
+
+    def get(self, language, name, docname):
+        name = f"{language}-{name}"
+        if name in self.entities[docname]:
+            return self.entities[docname][name]
+        elif name in self.entities[GLOBALNAME]:
+            return self.entities[GLOBALNAME][name]
+        else:
+            return None
+
+
+class EntitiesDirective(SphinxDirective):
+    has_content = True
+
+    def run(self):
+        content = nodes.definition_list()
+        self.state.nested_parse(self.content, self.content_offset, content)
+
+        try:
+            entities = AllEntities.install(self.env)
+            entities.extract(content, self.env.docname)
+        except Exception as err:
+            raise self.error(f'Malformed directive "entities": {err}')
+
+        return []
+
+
+def entity_role(name, rawtext, text, lineno, inliner, options={}, content=[]):
+    node = EntityNode()
+    node.entity = text
+
+    return [node], []
+
+
+def process_entity_nodes(app, doctree, docname):
+    """ Replace all the entities by their content """
+    env = app.builder.env
+
+    entities = AllEntities.install(env)
+    entities.resolve_pendings(app)
+
+    language = next(l for l in LANGUAGES if l in app.tags)
+    for node in doctree.traverse(EntityNode):
+        entity = entities.get(language, node.entity, docname)
+        if entity is None:
+            node.replace_self(nodes.Text(_(node.entity), _(node.entity)))
+            logger.warning(f'Entity "{node.entity}" has not been defined', location=node)
+        else:
+            node.replace_self(entity["content"])
+
+
+def purge_entities(app, env, docname):
+    """ Purge any entity that comes from the given docname """
+    entities = AllEntities.install(env)
+    entities.purge(docname)
+
+
+def merge_entities(app, env, docnames, other):
+    """ Merge multiple environment entities """
+    entities = AllEntities.install(env)
+    other_entities = AllEntities.install(other)
+    entities.merge(other_entities)
+
+
+def setup(app):
+    app.add_node(EntityNode)
+    app.add_node(EntitiesNode)
+    app.add_directive("entities", EntitiesDirective)
+    app.add_role("entity", entity_role)
+
+    app.connect("doctree-resolved", process_entity_nodes)
+    app.connect("env-merge-info", merge_entities)
+    app.connect("env-purge-doc", purge_entities)
+
+    return {
+        "version": "0.1",
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 6d6acc8e..d2fe98e4 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -10,9 +10,11 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-# import os
-# import sys
-# sys.path.insert(0, os.path.abspath('.'))
+import os
+import sys
+
+sys.path.insert(0, os.path.abspath("./_ext"))
+sys.path.insert(0, os.path.abspath("."))
 
 
 # -- Project information -----------------------------------------------------
@@ -21,6 +23,8 @@ project = "tokenizers"
 copyright = "2020, huggingface"
 author = "huggingface"
 
+languages = ["node", "rust", "python"]
+
 # The full version, including alpha/beta/rc tags
 release = "0.9.0"
 
@@ -30,7 +34,7 @@ release = "0.9.0"
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ["sphinx.ext.autodoc", "sphinx.ext.napoleon"]
+extensions = ["sphinx.ext.autodoc", "sphinx.ext.napoleon", "entities"]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]