reserved-word
A reserved word is used as a name or a head.
Words like to, if, list and by belong to the language, so they cannot name a field, a record type, a phrase head or a variable. The full list is in spec/01. Reserved words may appear as later words of a pattern, such as Send [m: msg] to [n: node].
Example
Check this program to see the diagnostic.
# package p
Node has
set list to 0
Diagnostic
p/p.synod:3:7: error[reserved-word]: "list" is a reserved word and cannot be a field
Fix
Choose a name that is not a reserved word.
# package p
Node has
set items to 0