More than 500 years after Spaniards first set out to colonise distant lands, guardians of Spanish from 22 countries have finally drawn up joint rules for a language spoken by more than 500 million people.

Spain's Royal Language Academy (RAE) appointed itself custodian of the Spanish language over three centuries ago and has affiliates in every Spanish-speaking country, but has long been felt to ignore how millions actually communicate between Tijuana and Tierra del Fuego in Latin America.

For instance, the RAE dictionary lists nine separate definitions of the word "taco" before finally coming to what 100 million Mexicans eat every day, as well as millions more around the world.

But the new grammar book launched yesterday in Madrid seeks to end these divisions after 11 years of consultation with other Spanish language academies, and it comes out 80 years after the previous edition.

"The new grammar book is inclusive because Spanish is inclusive," Ignacio Bosque, lead editor of the new book, said after the launch. "It would be a good idea to let ourselves be enriched by variety, that is one of the book's aims."

The first two volumes covering 4,000 pages of morphology and syntax went on sale in bookshops across Spain last Friday, but will have to wait until the New Year to appear in Latin America.

"The fact we know that in such a country this and that is said is an extraordinary achievement which tears down barriers to mutual understanding," said Humberto Lopez Morales, from Puerto Rico, who is secretary-general of the Association of Spanish Language Academies.

A third volume of the grammar, on phonetics and phonology, will come out within a few months, along with a DVD showing variations in the pronunciation, tone and rhythms of Spanish as it is spoken across different linguistic zones.

Those reluctant to part with €120 for the new grammar will have to wait until autumn 2010 for a paperback version.

Publishers Espasa say the new book has "been received with great enthusiasm", but have declined to give figures for sales or print runs.

For some academics who collaborated in the project, unity amongst Spanish speakers was needed to preserve the language itself.