diff --git a/docs/developer_guides/chap02_schema.md b/docs/developer_guides/chap02_schema.md
index afba3e1fc8..457a9af3df 100644
--- a/docs/developer_guides/chap02_schema.md
+++ b/docs/developer_guides/chap02_schema.md
@@ -84,7 +84,7 @@ Different index type uses different index params in construction and query. All
 
 ## IVF_FLAT
 
-**IVF** (*Inverted File*) is an index type based on quantization. It divides the points in space into `nlist` units by the clustering method. During searching vectors, it compares the distances between the target vector and the center of all the units, and then selects the `nprobe` nearest unit. Afterwards, it compares all the vectors in these selected cells to get the final result.
+**IVF** (*Inverted File*) is an index type based on quantization. It divides the points in space into `nlist` units by the clustering method. During searching vectors, it compares the distance between the target vector and the center of all units, and then selects the `nprobe` nearest unit. Afterwards, it compares all the vectors in these selected cells to get the final result.
 
 IVF_FLAT is the most basic IVF index, and the encoded data stored in each unit is consistent with the original data.