diff --git a/grammar/abnf-grammar.txt b/grammar/abnf-grammar.txt
index 364dc923f2..e25a8aef02 100644
--- a/grammar/abnf-grammar.txt
+++ b/grammar/abnf-grammar.txt
@@ -432,29 +432,31 @@ letter = uppercase-letter / lowercase-letter
 ; The following rules defines (ASCII) decimal, octal, and hexadecimal digits.
 ; Note that the latter are case-insensitive.
 
-digit = %x30-39   ; 0-9
+decimal-digit = %x30-39   ; 0-9
 
 octal-digit = %x30-37   ; 0-7
 
-hexadecimal-digit = digit / "a" / "b" / "c" / "d" / "e" / "f"
+hexadecimal-digit = decimal-digit / "a" / "b" / "c" / "d" / "e" / "f"
 
-; An identifier is a non-empty sequence of letters, digits, and underscores,
+; An identifier is a non-empty sequence of
+; letters, (decimal) digits, and underscores,
 ; starting with a letter.
 ; It must not be a keyword: this is an extra-grammatical requirement.
 ; It must also not be or start with `aleo1`,
 ; because that is used for address literals:
 ; this is another extra-grammatical requirement.
 
-identifier = letter *( letter / digit / "_" )
+identifier = letter *( letter / decimal-digit / "_" )
              ; but not a keyword or a boolean literal or aleo1...
 
 ; A package name consists of one or more segments separated by single dashes,
-; where each segment is a non-empty sequence of lowercase letters and digits.
+; where each segment is a non-empty sequence of
+; lowercase letters and (decimal) digits.
 ; Similarly to an identifier, a package name must not be a keyword
 ; and must not be or start with `aleo1`.
 
-package-name = lowercase-letter *( lowercase-letter / digit )
-               *( "-" 1*( lowercase-letter / digit ) )
+package-name = lowercase-letter *( lowercase-letter / decimal-digit )
+               *( "-" 1*( lowercase-letter / decimal-digit ) )
                ; but not a keyword or a boolean literal or aleo1...
 
 ; Note that, grammatically, identifiers are also package names.
@@ -464,10 +466,10 @@ package-name = lowercase-letter *( lowercase-letter / digit )
 
 annotation-name = "@" identifier
 
-; A natural (number) is a sequence of one or more digits.
+; A natural (number) is a sequence of one or more decimal digits.
 ; We allow leading zeros, e.g. `007`.
 
-natural = 1*digit
+natural = 1*decimal-digit
 
 ; An integer (number) is either a natural or its negation.
 ; We allow leading zeros also in negative numbers, e.g. `-007`.
@@ -503,10 +505,10 @@ product-group-literal = integer %s"group"
 boolean-literal = %s"true" / %s"false"
 
 ; An address literal starts with `aleo1`
-; and continues with exactly 58 lowercase letters and digits.
+; and continues with exactly 58 lowercase letters and (decimal) digits.
 ; Thus an address always consists of 63 characters.
 
-address-literal = %s"aleo1" 58( lowercase-letter / digit )
+address-literal = %s"aleo1" 58( lowercase-letter / decimal-digit )
 
 ; A character literal consists of an element surrounded by single quotes.
 ; The element is any character other than single quote or backslash,