We have all been misunderstood. You said one thing; someone heard something else; and whatever you were doing together either stopped or was misdirected after that, one party thinking the other meant something other than they did. This is common throughout human life, whether in the sciences or between managers and employees.
Consider a mother teaching a name to a child. The child saw the bird, and her mother gives her the word for it. Before she knew the name the child did not know what to call it, and that meant she could not ask questions about it or easily keep track of it over time. The child did not receive a physical bird from her mother; she received a way to speak about and investigate birds and relate them to other things.
Imagine an argument in which the participants go back and forth arguing for what each thinks to be true and they discover that the whole argument comes down to one word that they have not yet defined or a word of which they have different definitions. They were not, then, disagreeing about things but about words. They were either using one word for two things or two words for one thing. It is not until both have the same understanding of what the word means that they can make much progress.
Laws take the form of words and through them we know what we are allowed to do and what we cannot do, what we must do and what will take place in certain circumstances. Words and their meanings are crucial for the political and legal order, to say nothing of the wider social world.
Promises too take the form of words and through them our whole lives can be altered, from the promises made in marriage to the promise a soldier makes to serve his country for a set number of years. This is likewise true of prayers and petitions, of the exhortations a leader sometimes has to make and the sentence that a judge passes on a guilty man.
All our learning and all our theory begin from the words we use, what they mean, and what we do with them. A community of learners cannot even consider methodology, principles, or approach to a set of questions before it has a common language and a common way of understanding language, meaning, and truth, at least implicitly. The later sciences, the later arts, even the later piety of a tradition, all come about within the broad order of speech, words, meaning, and truth.
This is confirmed also historically: in every major classical culture, from China and India to the Ancient Near East and Greece, the first disciplines discovered and articulated and the disciplines that guide the others were all based on language, meaning, and truth, on names and terms, on sentences and texts.
By insisting on the fact that the best way to begin is with words, the classical tradition of the trivium does not place our private thoughts somehow as things that exist without language and that we later merely express in words or not, as we wish. Rather, the trivium begins from the fact that teaching, learning, promising, arguing, giving judgment, and articulating our thoughts in general are all necessary foundations for any higher study or cooperative effort. This is true even if we are only thinking of ourselves as individuals; as we shall see below, even the individual's own thoughts take form in words.
The claim that language is or could be somehow completely private, where each speaker has his own thoughts first without reference to language and only later comes to express them in words, is much closer to the modern tradition of philosophical speculation on the mind, especially, for example, in the work of thinkers like René Descartes and Francis Bacon. The account given by the classical trivium is outlined in How a word reaches a thing.
How words, concepts, and things actually relate to one another is a real question, but it is not the first question. The first question is simpler: What is the purpose or goal of language? Does it have more than one?
Continue to What language is for.