The core of a thing; the most essential or important part.(noun)
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Use "heart and soul" in a sentence
"It helps enormously that Jamie Salé is not a cynical girl, not at all, and that from the time she was very small, she has been unabashedly putting her heart and soul into everything she skates, from “Deep in the Heart of Texas” right up through Love Story."
"Aloha Quilt Camp offered an exciting opportunity, something new and promising, but she had put her heart and soul into Elm Creek Quilts."
"And it must be remembered that the original nine Templar knights had emerged from Languedocian culture, the heart and soul of the Magdalene cult—and that occult tradition has it that they learned their secrets ‘from the Johannites of the East’."