Any girl growing up in a town with a rhythmic name like Saskatoon, Saskatchewan, must either love or hate words. Joni Mitchell loves them.

Less singer than songwriter, less songwriter than poet, she has come from obscurity in the past two years to a prominence where practically everyone - from Frank Sinatra to Johnny Cash - records her compositions and where her own concerts and albums give her an income of $500,000 a year.

"My mother raised me on words," she says. "Where other parents would quote from the Bible, she would quote from Shakespeare. She was a romantic woman. She encouraged me in all those old-fashioned things. I kept pressed-flower scrapbooks."

In a sense, Joni Mitchell. now 25, still keeps pressed flowers. Her biggest hit, "Both Sides Now," is a lament for her broken marriage:

"Moons and Junes and ferris wheels
The dizzy dancing way you feel
As every fairy tale comes true
I've looked at love that way"
I've looked at love from both sides now
From give and take and still somehow
It's love's illusions I recall
I really don't know love at all."

A willowy, blonde girl with a shy manner masking a will like cool blue steel, Joni went through a long apprenticeship. At 19, she dropped out of art school and took a $15- a-week job in a Calgary coffee house "singing long tragic songs in a minor key."

A few months later, she made the three-day train journey to Toronto, wrote her first song (Day after Day) on the way, and then filled a succession of non-union gigs (she didn't have the $200 union fee) in church basements and YMCA meeting halls.

In Toronto she met a folk singer named Chuck Mitchell, married him 36 hours later, sang with him for the next two years:

"Marriage was good for us at the time, but it had to come to an end, I guess. We broke up the duo, and I guess the thing that busted it was when I started making more money. That hurt a lot, especially for two Scorpios. We're very proud people."

Joni moved to New York and hated it. She was mugged twice, robbed once; the crowds, the ugliness made her long for the country. With a stranger - a taxi driver - she had one of those casual, cruel encounters in which city life abounds:

"He asked me for a dollar more,
He cursed me to my face.
He hated everyone who paid to ride
And share his common space."

But she kept writing...and singing...and, almost without meaning to prospering. She formed her own publishing company, as one-woman an operation as is humanly possible these days. It is called Siquomb, an acronym from a fairyland of her own, meaning "She is queen undisputed of mind beauty."

Siquomb produces only Joni Mitchell songs, recorded by Joni Mitchell, who also paints the album covers and writes the liner notes. Recently, she was offered $1,500,000 for the company and rejected it. "If I'd taken it," she explains, "it would have been as if I'd done all the writing for money."

Whether this is feminine logic or the reasoning of some C.P.A. Joni today lives about as simply as a girl with half a million a year income could possibly live - in a modest alpine chalet in the West Hollywood Hills of Laurel Canyon.

She is surrounded by baroque and nouveau art objects, flowers, kittens and a lean young rock singer named Graham Nash.

She paints, she plans concert dates, she writes. Now she is working on a screenplay tentatively titled Willie and Ramone. Her first movie has been released: Arlo Guthrie's "Alice's Restaurant" in which she appears briefly singing her own "Songs to Aging Children Come."

"Joni has this fantastic drive to create all the time," says Nash. "If nothing constructive was done during the day, she feels dissatisfied. She's got to be doing something, even if it's making rhubarb pie."