diff --git a/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/i_deactivated_subdomain.md b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/i_deactivated_subdomain.md
new file mode 100644
index 0000000000000000000000000000000000000000..5c64bbd2f559d7b4b825455dec2265a9a7c6a1d9
--- /dev/null
+++ b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/i_deactivated_subdomain.md
@@ -0,0 +1,2 @@
+It defines a set of deactivated subdomains, which includes  a time interval and
+ material IDs.
diff --git a/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_material_ids.md b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_material_ids.md
new file mode 100644
index 0000000000000000000000000000000000000000..fef4b940d87f148cfb8154809b62921f8f6d6f97
--- /dev/null
+++ b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_material_ids.md
@@ -0,0 +1 @@
+Material IDs of a set of deactivated subdomains.
diff --git a/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_time_interval.md b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_time_interval.md
new file mode 100644
index 0000000000000000000000000000000000000000..c6052b5abbcbbda9bee4bc646e1acadc0fe4176b
--- /dev/null
+++ b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/deactivated_subdomain/t_time_interval.md
@@ -0,0 +1,4 @@
+The time interval of a set of deactivated subdomains.
+
+For its input syntax, please also see:
+\copydoc ogs_file_param__prj__time_loop__processes__process__time_interval
diff --git a/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/i_deactivated_subdomains.md b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/i_deactivated_subdomains.md
new file mode 100644
index 0000000000000000000000000000000000000000..4f14a8960fdd4b9dcc6571dca33d3e2df50a7683
--- /dev/null
+++ b/Documentation/ProjectFile/prj/process_variables/process_variable/deactivated_subdomains/i_deactivated_subdomains.md
@@ -0,0 +1,8 @@
+It defines sets of deactivated subdomains, each of which contains a time
+ interval and material IDs. When the time is in the time interval of a set of
+ deactivated subdomains, the elements in the deactivated subdomains are excluded
+ from the local and global assembly, and also from the computation of the
+ secondary variables.
+
+Note: the nodes at the borders among active subdomains and inactive subdomains
+ are included through the entire computations.