diff --git a/.vim/syntax/todo.vim b/.vim/syntax/todo.vim
index 2c0022b..d911365 100644
--- a/.vim/syntax/todo.vim
+++ b/.vim/syntax/todo.vim
@@ -95,6 +95,7 @@ highlight todoStatusQuestion ctermfg=darkcyan guifg=#6666ff
 syntax match timeslot "\v\[.*-.*\] " nextgroup=todoItem skipwhite
 highlight timeslot ctermfg=Magenta
 
+" A todoItem has a subject (e.g., a word that's followed by a ':')
 syn match todoItem '\i\+:' contained
 hi todoItem ctermfg=Blue