diff --git a/django/core/validators.py b/django/core/validators.py
index da1959c7d6..89568cfb05 100644
--- a/django/core/validators.py
+++ b/django/core/validators.py
@@ -234,6 +234,7 @@ validate_email = EmailValidator()
 slug_re = _lazy_re_compile(r'^[-a-zA-Z0-9_]+\Z')
 validate_slug = RegexValidator(
     slug_re,
+    # Translators: "letters" means latin letters: a-z and A-Z.
     _("Enter a valid 'slug' consisting of letters, numbers, underscores or hyphens."),
     'invalid'
 )