diff --git a/spec/06_API_specification/02_column_selection.md b/spec/API_specification/column_selection.md
similarity index 100%
rename from spec/06_API_specification/02_column_selection.md
rename to spec/API_specification/column_selection.md
diff --git a/spec/06_API_specification/01_dataframe_basics.md b/spec/API_specification/dataframe_basics.md
similarity index 100%
rename from spec/06_API_specification/01_dataframe_basics.md
rename to spec/API_specification/dataframe_basics.md
diff --git a/spec/06_API_specification/03_filter_rows.md b/spec/API_specification/filter_rows.md
similarity index 100%
rename from spec/06_API_specification/03_filter_rows.md
rename to spec/API_specification/filter_rows.md
diff --git a/spec/06_API_specification/index.rst b/spec/API_specification/index.rst
similarity index 60%
rename from spec/06_API_specification/index.rst
rename to spec/API_specification/index.rst
index d87dba63..d8a9dddb 100644
--- a/spec/06_API_specification/index.rst
+++ b/spec/API_specification/index.rst
@@ -5,6 +5,6 @@ API specification
    :caption: API specification
    :maxdepth: 1
 
-   01_dataframe_basics
-   02_column_selection
-   03_filter_rows
+   dataframe_basics
+   column_selection
+   filter_rows
diff --git a/spec/03_assumptions.md b/spec/assumptions.md
similarity index 100%
rename from spec/03_assumptions.md
rename to spec/assumptions.md
diff --git a/spec/09_benchmark_suite.md b/spec/benchmark_suite.md
similarity index 100%
rename from spec/09_benchmark_suite.md
rename to spec/benchmark_suite.md
diff --git a/spec/04_design_topics/backwards_compatibility.md b/spec/design_topics/backwards_compatibility.md
similarity index 100%
rename from spec/04_design_topics/backwards_compatibility.md
rename to spec/design_topics/backwards_compatibility.md
diff --git a/spec/04_design_topics/data_interchange.md b/spec/design_topics/data_interchange.md
similarity index 100%
rename from spec/04_design_topics/data_interchange.md
rename to spec/design_topics/data_interchange.md
diff --git a/spec/04_design_topics/index.rst b/spec/design_topics/index.rst
similarity index 100%
rename from spec/04_design_topics/index.rst
rename to spec/design_topics/index.rst
diff --git a/spec/05_future_API_evolution.md b/spec/future_API_evolution.md
similarity index 100%
rename from spec/05_future_API_evolution.md
rename to spec/future_API_evolution.md
diff --git a/spec/index.rst b/spec/index.rst
index 8663f136..c14ab8d0 100644
--- a/spec/index.rst
+++ b/spec/index.rst
@@ -8,22 +8,22 @@ Contents
    :caption: Context
    :maxdepth: 1
 
-   01_purpose_and_scope
-   02_use_cases
-   03_assumptions
+   purpose_and_scope
+   use_cases
+   assumptions
 
 .. toctree::
    :caption: API
    :maxdepth: 1
 
-   04_design_topics/index
-   05_future_API_evolution
-   06_API_specification/index
+   design_topics/index
+   future_API_evolution
+   API_specification/index
 
 .. toctree::
    :caption: Methodology and Usage
    :maxdepth: 1
 
-   07_usage_data
-   08_verification_test_suite
-   09_benchmark_suite
+   usage_data
+   verification_test_suite
+   benchmark_suite
diff --git a/spec/01_purpose_and_scope.md b/spec/purpose_and_scope.md
similarity index 100%
rename from spec/01_purpose_and_scope.md
rename to spec/purpose_and_scope.md
diff --git a/spec/07_usage_data.md b/spec/usage_data.md
similarity index 100%
rename from spec/07_usage_data.md
rename to spec/usage_data.md
diff --git a/spec/02_use_cases.md b/spec/use_cases.md
similarity index 100%
rename from spec/02_use_cases.md
rename to spec/use_cases.md
diff --git a/spec/08_verification_test_suite.md b/spec/verification_test_suite.md
similarity index 100%
rename from spec/08_verification_test_suite.md
rename to spec/verification_test_suite.md