determines->determine for plural in why concepts important section.

docs/content/concepts/layer/validation/_index.md

@@ -16,7 +16,7 @@ If you are not an OSCAL tool developer, this technical information might be usef
 
 It is important that OSCAL tool developers use specialized software to confirm that JSON-, XML-, or YAML-based [OSCAL document instances](/concepts/layer/) are  well-formed and valid.
 
-Generally, both "well-formedness" and "validity" of OSCAL instance data determines if a conformant OSCAL application can process this data. In this way, "well-formedness" and "validity" define the boundary between what can be considered OSCAL data or not. The degree to which an application can support well-formed, valid OSCAL data defines how conformant the application is.
+Generally, both "well-formedness" and "validity" of OSCAL instance data determine if a conformant OSCAL application can process this data. In this way, "well-formedness" and "validity" define the boundary between what can be considered OSCAL data or not. The degree to which an application can support well-formed, valid OSCAL data defines how conformant the application is.
 
 ## What do "well-formed" and "valid" mean to the OSCAL community?