Definition of "Multilingualism"

As it was stated in previous chapter, multilingualism is an extremely broad notion at the present moment that is not a subject to the easy way of concept definition. At any rate, we should try hard to determine its definition in order to be able to understand all the below-mentioned multilingual phenomena in a better way. In other words, we should do our best to figure out the core of this notion.
Here we may refer to several sources in order to find out the "golden middle" of all viewed definitions and something that doesn't escape any of them.
According to Merriam-Webster Online Dictionary, "multilingualism" may be distinguished in two possible ways: "something expressed in several languages" or "a person using or able to use several languages with equal fluency".
Under Wiktionary, "multilingualism" is "the condition of being able to speak several languages".
In obedience to the Oxford Advanced Learner's Dictionary, "multilingual" means "speaking or using many languages" or "written or printed in many languages.
So, we have three different definitions which draw a similar line at the same time. Anyway, we have the phrase of "several or many languages" inside all characterizations and "able to speak (communicate) in them". So, the conclusion we may arrive at is that multilingualism is a more social (related to people) than scientific phenomenon that requires serious and fundamental research simultaneously.
In below-mentioned chapters we analyze multilingualism and bilingualism (as it's the most widely-spread form) in different aspects including social, personal, IT and psychological.