Monastic Sign Language was not only useful because it allowed for silent communication, it also helped monks from different countries communicate with each other! It was what we call a lingua franca, which is what we call the language that two parties use when neither speak each other's mother tongue. In case your native language isn't English, we are using English as a lingua franca right now! Perhaps you are also familiar with Esperanto, which was invented with the idea of being a universal lingua franca.
Monastic Sign Language had a hand alphabet, just like natural sign languages (those used by Deaf communities). This allowed monks to spell out words they didn't have signs for, like each other's names.
They also had their own counting system! They could use two hands to count up to a million, although their strategies for doing so were a bit complicated sometimes.
'Monastic Sign Language' is actually a bit of a misnomer for two reasons:
Monastic Sign Language is technically not a complete language, so we call it a communication system instead. That is because of multiple reasons: it doesn't have a lot of signs, it borrows a lot from the monks' spoken languages, and it is not learned as a first language or transmitted from generation to generation. In fact, 10 0 % of its users are second-language learners, which is quite unique!
Monastic Sign Language is not really one language, but actually a collection of different dialects and regional variants. They all originate from the monastery in Cluny, France, but after hundreds of years of change they've all become quite different from one another.
Monastic Sign Language allows for extremely long compounds (words that stick together to become a new word, like blackboard in English). For example, the sign for 'curry rice' in a Japanese monastery exists of: TURBAN + POWDER + JAPANESE + BEAN + EAT
Monastic Sign Language 