Nancy Mairs, whose encounters with mental illness, disease and religious faith found expression in a series of trenchant, intensely personal essays and memoirs, died on Saturday at her home in Tucson. She was 73.

George Mairs, her husband, said that the cause had not been determined, but that Ms. Mairs had struggled with multiple sclerosis for more than 40 years and had relied on a wheelchair since 1993.

Ms. Mairs was a budding poet in her late 20s, suffering from agoraphobia and depression — she had once attempted suicide — when she was told that she had M.S. The inexorable progress of the disease provided her with her richest subject, as she wrote of her fears and hopes, her resolve to push against her limitations and her aversion to such euphemisms as “differently abled.”

“I refuse to participate in the degeneration of the language to the extent that I deny that I have lost anything in the course of this calamitous disease; I refuse to pretend that the only differences between you and me are the various ordinary ones that distinguish any one person from another,” she wrote in the introduction to “Plaintext: Deciphering a Woman’s Life” (1986), the essay collection that established her as a fierce, funny, feminist voice. Her essays “On Being a Cripple” and “Sex and the Gimpy Girl” made the point, defiantly.