11th commandment
eleventh commandment → 11η εντολή, ενδεκάτη εντολή, εντέκατη εντολή, απαράβατος κανόνας
Eleventh Commandment
(idiomatic) A well-known convention (often the most well-known of a certain field) which supposedly can not or should not be broken.
11th commandment - Wiktionary