diff --git a/src/aac_metrics/classes/vocab.py b/src/aac_metrics/classes/vocab.py
index 6b1c474..f6c70b5 100644
--- a/src/aac_metrics/classes/vocab.py
+++ b/src/aac_metrics/classes/vocab.py
@@ -71,6 +71,7 @@ def get_output_names(self) -> tuple[str, ...]:
             "vocab.precision",
             "vocab.recall",
             "vocab.f1",
+            "vocab.jaccard",
         )
 
     def reset(self) -> None:
diff --git a/src/aac_metrics/functional/vocab.py b/src/aac_metrics/functional/vocab.py
index a31cc08..f207d56 100644
--- a/src/aac_metrics/functional/vocab.py
+++ b/src/aac_metrics/functional/vocab.py
@@ -80,11 +80,14 @@ def vocab(
             token for refs in tok_mrefs for ref in refs for token in ref
         )
 
-        tp = corpus_vocab_cands.intersection(corpus_vocab_mrefs)
-        fn = corpus_vocab_mrefs.difference(corpus_vocab_cands)
-        vocab_precision = len(tp) / len(corpus_vocab_cands)
-        vocab_recall = len(tp) / (len(tp) + len(fn))
+        inter = corpus_vocab_cands.intersection(corpus_vocab_mrefs)  # True positives
+        diff = corpus_vocab_mrefs.difference(corpus_vocab_cands)  # False negatives
+        union = corpus_vocab_cands.union(corpus_vocab_mrefs)
+
+        vocab_precision = len(inter) / len(corpus_vocab_cands)
+        vocab_recall = len(inter) / (len(inter) + len(diff))
         vocab_f1 = 2 * vocab_precision * vocab_recall / (vocab_precision + vocab_recall)
+        vocab_jaccard = len(inter) + len(union)
 
         vocab_mrefs_len_full = _corpus_vocab_size(
             [ref for refs in tok_mrefs for ref in refs], dtype
@@ -128,6 +131,7 @@ def vocab(
             "vocab.precision": vocab_precision,
             "vocab.recall": vocab_recall,
             "vocab.f1": vocab_f1,
+            "vocab.jaccard": vocab_jaccard,
         }
 
     vocab_outs = corpus_scores, sents_scores