Update glossary

content/en/getting-started/glossary.md

@@ -92,6 +92,10 @@ Used within a [template action](#template-action), a function takes one or more
 
 Metadata at the beginning of each content page, separated from the content by format-specific delimiters. See [details](/content-management/front-matter/).
 
+### identifier
+
+An string that represents a variable, method, object, or field. It must conform to Go's [language specification](https://go.dev/ref/spec#Identifiers), beginning with a letter or underscore, followed by zero or more letters, digits, or underscores.
+
 ### int
 
 See [integer](#integer).