Over the years, Maggie Smith has played the dithering and the withering, the brilliant and the mundane, making it all look effortless. Who doesn't want to watch that?

In recent years, she has specialized in sharp-tongued, perpetually appraising women whose implacable gaze and scathingly insightful retorts shield, one suspects, a heart broken young. Even before she began playing the redoubtable Professor McGonagall in the Harry Potter series, she could freeze a room with a look, orate in a perfectly timed silence, break your heart by simply squaring her shoulders or settling her shawl.

It's been a big year for Smith, even by her perpetually prolific and wide-ranging standards. In "The Best Exotic Marigold Hotel," she played a chronically dissatisfied former domestic worker without, initially, a kind word for anyone; in the newly released "Quartet," she is an opera diva who brings her outsized sense of self to rest among a group of friends at a retirement community. She's already received six nominations this awards season — four from the Screen Actors Guild and two Golden Globe nods.

In "Downton Abbey," she is the dowager countess of Grantham, a woman who says whatever she thinks to whomever she pleases. In Season 1 especially, she was the most formidable, and entertaining, symbol of a class system collapsing under the weight of its own absurdity.

"What is a 'week-end'?" she asked the middle-class lawyer set, through the vagaries of British law, to inherit Downton. She gave the final word the careful and slightly disparaging intonation usually reserved for questionable nouns in a foreign language.

It was a glorious moment; the tone for the entire series set in a single word. Many rhapsodize the sibilance and hard consonants of fellow "Potter" castmate Alan Rickman, but no one enunciates like Maggie Smith; if anyone can pronounce the word "glacial" with more narcissism-baring deliciousness than she did in "Gosford Park," I'll eat my tiara.

In her hands, sentences are as much sound effect, or in some cases, scores, as they are dialogue; she clatters and clips, slurs and simpers, dipping into this octave and that with the agility of an opera star. "Oh, Peter," she sighs, as the grown-old Wendy in "Hook," and suddenly that film is a lament for both age and youth.

Like Angela Lansbury, whom the multitudes will also watch in anything, Smith is one of those women who has looked essentially the same since she was 20, whom age has burnished rather than diminished. In a face softened and unapologetically lined, those prominent blue eyes, that expressive slice of a mouth are even more arresting.

When she chooses, Maggie Smith remains one of an ever-diminishing number of women to whom the term "commanding" can accurately be applied. Americans have always been soft, but the modern relaxation of social strait-lacing has made its way to Britain, where "Iron Lady" Margaret Thatcher was replaced by People's Princess Dianaand now beloved commoner Kate Middleton.

As middle age expands to encompass pretty much any number between 40 and death, the ramrod stiffness of spine and expectation that once marked the elderly matriarch or dowager are quickly becoming antique, the rigors of posture no longer necessary in a world supported by Spanx. Smith, and a few of her peers, still have enough muscle memory to evoke these female pillars of Freudian nightmare and great literature, women of principle and control, who may actually understand the tyranny and contradiction of their particular social order but who believe that the chaotic alternative will be, in the end, much worse.

For better and worse, they are disappearing. These women ruled families without raising their voices; they ungently tried to prevent the follies of youth and considered snobbery not just a necessary sorting of the world but a sign of intelligence. With her double-edged smiles, quicksilver timing and easy service of backhand compliments, Smith not only keeps them vivid but also offers a master class to a younger generation of performers.

There comes a point in a truly great actor's career when he or she is both utterly immersed in character and instantly recognizable as personal presence. Watching Maggie Smith do just about anything — and she is also one of the more prolific and varied performers around — one is compelled to sit up a little straighter; to speak a bit more clearly; to calculate, without appearing to, the melody of the conversation, the mood of the room.

She makes it look so effortless, she always has — the lift of an eyebrow, the tilt of her chin, and the world cracks open in her hand.

Who doesn't want to watch something like that?