Bone density: How thick/heavy/tightly packed with minerals your bones are. The more tightly packed—the denser your bones—the stronger they are, and the less likely to break. When bone density falls below a certain level, you have osteoporosis.

DEXA scan: Dual Energy X-ray Absorptiometry, the most common, and one of the most accurate ways to measure bone density.

If you’re any woman approaching age 65; a younger, post-menopausal women with osteoporosis risk factors (e.g., family history);...