diff --git a/cf_pandas/__init__.py b/cf_pandas/__init__.py
index 4c249a8..2638fa9 100644
--- a/cf_pandas/__init__.py
+++ b/cf_pandas/__init__.py
@@ -8,7 +8,7 @@
 from .options import set_options  # noqa
 from .reg import Reg
 from .utils import always_iterable, astype, match_criteria_key, standard_names
-from .vocab import Vocab
+from .vocab import Vocab, merge
 from .widget import Selector, dropdown
 
 
diff --git a/cf_pandas/vocab.py b/cf_pandas/vocab.py
index 0574322..bd8568c 100644
--- a/cf_pandas/vocab.py
+++ b/cf_pandas/vocab.py
@@ -4,7 +4,7 @@
 import pathlib
 
 from collections import defaultdict
-from typing import DefaultDict, Dict, Optional, Union
+from typing import DefaultDict, Dict, Optional, Sequence, Union
 
 from .utils import astype
 
@@ -51,22 +51,37 @@ def make_entry(
         expressions = astype(expressions, list)
         entry: DefaultDict[str, Dict[str, str]] = defaultdict(dict)
         entry[nickname][attr] = "|".join(expressions)
-        self.__add__(entry)
+        self.__iadd__(entry)
 
-    def __add__(self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"]):
+    def add(
+        self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"], method: str
+    ) -> "Vocab":
         """Add two Vocab objects together...
 
         by adding their `.vocab`s together. Expressions are piped together but otherwise not changed.
+        This is used for both `__add__` and `__iadd__`.
 
         Parameters
         ----------
         other_vocab: Vocab
             Other Vocab object to combine with.
+        method : str
+            Whether to run as "add" which returns a new Vocab object or "iadd" which adds to the original object.
+
+        Returns
+        -------
+        Vocab
+            vocab + other_vocab either as a new object or in place.
         """
 
         if isinstance(other_vocab, Vocab):
             other_vocab = other_vocab.vocab
 
+        if method == "add":
+            output = Vocab()
+        elif method == "iadd":
+            output = self
+
         nicknames = set(list(self.vocab.keys()) + list(other_vocab.keys()))
         for nickname in nicknames:
 
@@ -82,8 +97,22 @@ def __add__(self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"])
                     + "|"
                     + other_vocab[nickname].get(attribute, "")
                 ).strip("|")
-                self.vocab[nickname][attribute] = new_expressions
-        return self
+                output.vocab[nickname][attribute] = new_expressions
+        return output
+
+    def __add__(self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"]):
+        """vocab1 + vocab2"""
+        return self.add(other_vocab, "add")
+
+    def __iadd__(self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"]):
+        """vocab1 += vocab2"""
+        return self.add(other_vocab, "iadd")
+
+    def __radd__(
+        self, other_vocab: Union[DefaultDict[str, Dict[str, str]], "Vocab"]
+    ) -> "Vocab":
+        """right add?"""
+        return self.__add__(other_vocab)
 
     def save(self, savename: Union[str, pathlib.PurePath]):
         """Save to file.
@@ -108,3 +137,23 @@ def open_file(self, openname: Union[str, pathlib.PurePath]):
         return json.loads(
             open(pathlib.PurePath(openname).with_suffix(".json"), "r").read()
         )
+
+
+def merge(vocabs: Sequence[Vocab]) -> Vocab:
+    """Add together multiple Vocab objects.
+
+    Parameters
+    ----------
+    vocabs : Sequence[Vocab]
+        Sequence of Vocab objects to merge.
+
+    Returns
+    -------
+    Vocab
+        Single Vocab object made up of input vocabs.
+    """
+
+    final_vocab = Vocab()
+    for vocab in vocabs:
+        final_vocab += vocab
+    return final_vocab
diff --git a/docs/demo_vocab.md b/docs/demo_vocab.md
index e370eda..113d784 100644
--- a/docs/demo_vocab.md
+++ b/docs/demo_vocab.md
@@ -6,7 +6,7 @@ jupytext:
     format_version: 0.13
     jupytext_version: 1.14.0
 kernelspec:
-  display_name: Python 3 (ipykernel)
+  display_name: Python 3.10.6 ('cf-pandas')
   language: python
   name: python3
 ---
@@ -139,6 +139,19 @@ vocab2.make_entry("other_variable_nickname", "match_that_string", attr="standard
 vocab1 + vocab2
 ```
 
+Merge 2 or more Vocab objects:
+
+```{code-cell} ipython3
+cfp.merge([vocab1, vocab2])
+```
+
+Can also add in place
+
+```{code-cell} ipython3
+# also works
+vocab1 += vocab2
+```
+
 ## Use the `Reg` class to write regular expressions
 
 We used simple exact matching regular expressions above, but for anything more complicated it can be hard to write regular expressions. You can use the `Reg` class in `cf-pandas` to write regular expressions with several options, as demonstrated more in [another doc page](https://cf-pandas.readthedocs.io/en/latest/demo_reg.html), and briefly here.
diff --git a/tests/test_vocab.py b/tests/test_vocab.py
index ebcb6d6..ffe4e09 100644
--- a/tests/test_vocab.py
+++ b/tests/test_vocab.py
@@ -20,19 +20,27 @@ def test_make_entry():
 
 def test_add_vocabs():
     vocab = cfp.Vocab()
-    vocab.make_entry("temp", ["a", "b"], attr="standard_name")
-    vocab.make_entry("salt", ["a", "b"], attr="name")
+    vocab.vocab = defaultdict(
+        dict, {"temp": {"standard_name": "a|b"}, "salt": {"name": "a|b"}}
+    )
     compare = {"temp": {"standard_name": "a|b|a|b"}, "salt": {"name": "a|b|a|b"}}
     assert (vocab + vocab).vocab == compare
 
     vocab2 = cfp.Vocab()
-    vocab2.make_entry("temp", ["a", "b"], attr="name")
+    vocab2.vocab = defaultdict(dict, {"temp": {"name": "a|b"}})
     compare = {
-        "temp": {"name": "a|b", "standard_name": "a|b|a|b"},
-        "salt": {"name": "a|b|a|b"},
+        "temp": {"standard_name": "a|b", "name": "a|b"},
+        "salt": {"name": "a|b"},
     }
     assert (vocab + vocab2).vocab == compare
 
+    # also merge
+    assert cfp.merge([vocab, vocab2]).vocab == compare
+
+    # also iadd
+    vocab += vocab2
+    assert vocab.vocab == compare
+
 
 def test_make_more_entries():
     vocab = cfp.Vocab()