The study investigates the rule of spelling the root -ravn-/-rovn- and is considered to be a fragment of the academic description of Russian spelling, which is currently being under investigation at the Russian Language Institute of the Russian Academy of Sciences. The authors clarify the meanings that determine the spelling of the unstressed root, supplement the lists of exceptions, denote words with meanings not corresponding to the given values-criteria, and, for the first time in linguistics, investigate the words that can be correlated with different values-criteria, that is, they have double motivation. The rule codifies the spelling of words that have double motivation and fluctuate in usus, dictionaries, study guides and reference books. Spelling recommendations for these words correspond to the current linguistic norm and were approved by the Spelling Commission of the Russian Academy of Sciences in 2019. The linguistic commentary to the rule contains the most significant etymological facts concerning the root -ravn-/-rovn- and summarises the scientific and methodological attempts to figure out the distribution of vocabulary with root -ravn-/-rovn- based on the meanings selected in the spelling rules. In the paper it is shown that the instability in spelling of various verbs with the root -ravn-/-rovn- in modern writing and dictionaries is determined by the double motivation of words, as well as contradictory recommendations and gaps in the rules.