NEW YORK (NYT NEWS SERVICE ).- This morning, a couple stood outside my window, arguing.

“What does that mean?” the woman kept saying. “What does that even mean?”

“It doesn’t mean anything,” the man kept responding. “Listen to what I am saying. You know what I’m saying.”

“What does that mean?” she said, and finally, with dangerous composure: “I’m so glad we had this conversation.”

It’s astonishing that humans are expected to make our way in the world with language alone. “To speak is an incomparable act / of faith,” the poet Craig Morgan Teicher has written. “What proof do we have / that when I say mouse, you do not think / of a stop sign?”

“Don’t Believe a Word,” a new book by Guardian writer and editor David Shariatmadari, delves into the riddles of language: the opacities, ambushes, dead ends, sudden ecstasies. It’s a brisk and friendly introduction to linguistics, and a synthesis of the field’s recent discoveries. So much more is now known about how language evolves, how animals communicate and how children learn to speak. Such findings remain mostly immured in the academy, however. Our “insatiable appetite for linguistic debate,” Shariatmadari writes, is born out of confusion. “Why do millennials speak their own language? Do the words they choose reflect the fact that they are superficial, lazy, addicted to technology? How can you protect a language against outside influence? Does the language we use to talk about climate change, or Brexit, change the way we think about them?”

Shariatmadari organizes his book around a few core misapprehensions, taking decisive aim at some well-chosen foes. Enemy Number One: The pedant or self-styled grammar snob, who has been with us for at least 400 years judging by the examples presented here, wringing his hands and lamenting the decline in linguistic standards. “Even though the idea that language is going to the dogs is widespread, nothing much has been done to mitigate it,” Shariatmadari writes. “It’s a powerful intuition, but the evidence of its effects has simply never materialized. That is because it is unscientific nonsense.”

The expressive power of language is undiminished, but human communication is in constant flux and ought to be understood, this book argues, as “a snapshot” of a time, place and particular community of speakers. Even the simplest words alter with time. “Adder,” “apron” and “umpire,” for example, were originally “nadder,” “napron” and “numpire.” Bird used to be “brid,” and “horse,” “hros,” transpositions of letters that later became the norm. “Empty” used to be “emty” — a transformation that reveals physics at work, according to Shariatmadari. “The simple mechanics of moving from a nasal sound (‘m’ or ‘n’) to a non-nasal one can make a consonant pop up in between” — in this case, the “p” sound we hear.

Our bodies drive these changes, as do our yearnings for status and belonging. Members of a community in Papua New Guinea were found to have flipped the masculine and feminine gender agreements to distinguish themselves from the neighboring tribes, with which they shared a language. A study of Martha’s Vineyard in the 1960s found that longtime residents were unconsciously adopting an accent to separate themselves from summer visitors.

Of all the factors that transform how we communicate, none are so powerful as young people, who have always steered language. They remake it as they learn it, inducing in older people a powerful sense of “linguistic disorientation.” (Symptoms include petulant tweets and letters to the editor.)

To speak about language is always to speak about power. There is the power of linguistic innovation, which is often met by the powers of stigma and contempt, of racism and class prejudice. Perhaps no dialect has come under more hysterical attack than African American Vernacular English (AAVE). In the book’s strongest section, Shariatmadari reveals how little the so-called guardians of the English language understand about English, let alone the particular innovations of AAVE, which linguists have described as a rule-bound language that has given us at least one new verb tense.

The scope of “Don’t Believe a Word” is impressive. It pauses to consider what modes of communication can tell us about the working of the brain, its role in communal violence in India and whether some languages are genuinely richer, more expressive or efficient. Shariatmadari is an earnest writer — clarity, not style, is his priority — but the quirks of human and animal speech are strange and alluring enough to leaven the narrative. Who knew that dolphins had accents?

It’s curious, however, that a writer so word-besotted should have such a blind spot for literature. Of course young people break and remake language. But so do poets. John Berryman was much on my mind as I read this book: “Nouns, verbs do not exist for what I feel,” he wrote in “Epilogue.” So was Emily Dickinson’s splayed syntax and idiosyncratic punctuation, and the experimentations of Paul Celan, who once wrote to his wife from Germany: “The language with which I make my poems has nothing to do with one spoken here, or anywhere.”

Nor does this book explore some of the knottier questions it so tantalizingly dangles. How does language shape (or even impede) our understanding of Brexit and climate change? Shariatmadari also introduces Noam Chomsky’s point that most human speech is internal and exists as thought, but doesn’t wrestle with what we know (what we can know) about its evolution. Are the shape and structure of our thoughts as prone to rapid reinvention as verbal and written communication?

In providing the reader a foundation in rudimentary linguistics and its history, Shariatmadari is perhaps prompting — even inducting — us into thinking through such issues ourselves. I can echo my agitated neighbor: I am glad to have had this conversation.

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