diff --git a/Metadata-standard-names.md b/Metadata-standard-names.md
index 346defa..3ee0032 100644
--- a/Metadata-standard-names.md
+++ b/Metadata-standard-names.md
@@ -732,9 +732,9 @@ Note that appending '_on_previous_timestep' to standard_names in this section yi
     * `real`: units = kg kg-1
 * `mass_fraction_of_dust_accumulation_aerosol_particles_in_air`: Mass fraction of accumulation mode dust aerosol particles
     * `real`: units = kg kg-1
-* `number_fraction_of_coarse_aerosol_particles_in_air`: Ratio of number concentration of coarse mode dust aerosol particles to the molecular concentration of air
+* `number_fraction_of_coarse_aerosol_particles_in_air`: Ratio of number concentration of coarse-mode dust aerosol particles to the molecular concentration of air; i.e., the ratio of the number of coarse-mode dust aerosol particles to the number of air molecules in a unit volume
     * `real`: units = particles molecules-1
-* `number_fraction_of_accumulation_aerosol_particles_in_air`: Ratio of number concentration of accumulation mode dust aerosol particles to the molecular concentration of air
+* `number_fraction_of_accumulation_aerosol_particles_in_air`: Ratio of number concentration of accumulation-mode dust aerosol particles to the molecular concentration of air; i.e., the ratio of the number of accumulation-mode dust aerosol particles to the number of air molecules in a unit volume
     * `real`: units = particles molecules-1
 ## emissions
 Emissions variables, contributed for the Community Emissions Data System (CEDS)
diff --git a/Metadata-standard-names.yaml b/Metadata-standard-names.yaml
index 14287b0..d0a0641 100644
--- a/Metadata-standard-names.yaml
+++ b/Metadata-standard-names.yaml
@@ -1178,14 +1178,16 @@ sections:
     kind: null
     units: kg kg-1
   - name: number_fraction_of_coarse_aerosol_particles_in_air
-    description: Ratio of number concentration of coarse mode dust aerosol particles
-      to the molecular concentration of air
+    description: Ratio of number concentration of coarse-mode dust aerosol particles
+      to the molecular concentration of air; i.e., the ratio of the number of coarse-mode
+      dust aerosol particles to the number of air molecules in a unit volume
     type: real
     kind: null
     units: particles molecules-1
   - name: number_fraction_of_accumulation_aerosol_particles_in_air
-    description: Ratio of number concentration of accumulation mode dust aerosol particles
-      to the molecular concentration of air
+    description: Ratio of number concentration of accumulation-mode dust aerosol particles
+      to the molecular concentration of air; i.e., the ratio of the number of accumulation-mode
+      dust aerosol particles to the number of air molecules in a unit volume
     type: real
     kind: null
     units: particles molecules-1
diff --git a/standard_names.xml b/standard_names.xml
index 6390bea..4dccf78 100644
--- a/standard_names.xml
+++ b/standard_names.xml
@@ -1370,11 +1370,11 @@
       <type units="kg kg-1">real</type>
     </standard_name>
     <standard_name name="number_fraction_of_coarse_aerosol_particles_in_air"
-                   description="Ratio of number concentration of coarse mode dust aerosol particles to the molecular concentration of air">
+                   description="Ratio of number concentration of coarse-mode dust aerosol particles to the molecular concentration of air; i.e., the ratio of the number of coarse-mode dust aerosol particles to the number of air molecules in a unit volume">
       <type units="particles molecules-1">real</type>
     </standard_name>
       <standard_name name="number_fraction_of_accumulation_aerosol_particles_in_air"
-                   description="Ratio of number concentration of accumulation mode dust aerosol particles to the molecular concentration of air">
+                   description="Ratio of number concentration of accumulation-mode dust aerosol particles to the molecular concentration of air; i.e., the ratio of the number of accumulation-mode dust aerosol particles to the number of air molecules in a unit volume">
       <type units="particles molecules-1">real</type>
     </standard_name>
   </section>