Clarity

Co-authored-by: Sadie L. Bartholomew <[email protected]>

appa.adoc

@@ -16,7 +16,7 @@ For variable attributes, the possible values of "Use" are:
 * **M** for geometry container variables,
 * **Do** for domain variables,
 * **BI** and **BO** for boundary variables (see <<cell-boundaries>> for the distinction between **BI** and **BO**),
-* **A** for an aggregation variable (see <<aggregation-variables>>),
+* **A** for aggregation variables (see <<aggregation-variables>>),
 * **-** for variables with some other purpose.
 
 CF does not prohibit any of these attributes from being attached to variables of different kinds from those listed as their "Use" in this table, but their meanings are not defined by CF if they are used in these other ways.