In 12.1. Configure a mod_cluster Worker Node there is "A mod_cluster worker node consists of an JBoss EAP server", but there should be "a" instead of "an".
Moving to ON_QA. The changes should be available for review on the documentation stage within an hour or so from this comment. http://documentation-devel.engineering.redhat.com/site/documentation/en-US/JBoss_Enterprise_Application_Platform/
Verified on stage.