vitamin D

noun

: any or all of several fat-soluble vitamins chemically related to steroids, essential for normal bone and tooth structure, and found especially in fish-liver oils, egg yolk, and milk or produced by activation (as by ultraviolet irradiation) of sterols: such as
a
or vitamin D2
-ˈdē-ˈtü How to pronounce vitamin D (audio)
: calciferol
b
or vitamin D3
-ˈdē-ˈthrē How to pronounce vitamin D (audio)
: cholecalciferol

Examples of vitamin D in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
With cold and flu season approaching, there’s lots of chatter about whether vitamin C or vitamin D is better for fighting off infections. — Jamie Ducharme, HEALTH, 19 Aug. 2026 The primary effect of vitamin D is to improve the secretion of insulin by beta-cells in the pancreas, according to Anastassios Pittas, MD, senior author of the study and chief of Endocrinology, Diabetes and Metabolism at Tufts Medical Center. — Fran Kritz, Verywell Health, 15 Aug. 2026 Patients should also ensure proper nutrition, following diets high in protein, calcium, vitamin D, and magnesium to promote muscle and bone health. — Jessica Starr, Fortune, 14 Aug. 2026 Whether that category expands beyond vitamin D stimulation will be determined by larger independent trials and real-world outcomes. — Tanya Akim, Forbes.com, 12 Aug. 2026 See All Example Sentences for vitamin D

Word History

First Known Use

circa 1921, in the meaning defined above

Time Traveler
The first known use of vitamin D was circa 1921

Rhymes for vitamin D

See All Rhymes for vitamin D

Browse Nearby Words

vitamin C
vitamin D
vitamin E
See all Nearby Words

Cite this Entry

“Vitamin D.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/vitamin%20D. Accessed 24 Aug. 2026.

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Kids Definition

vitamin D

noun
: any of several vitamins that are needed for normal bone and tooth structure, and are found especially in fish-liver oils, egg yolk, and milk or are produced in response to ultraviolet light

Medical Definition

vitamin D

noun
: any or all of several fat-soluble vitamins chemically related to steroids, essential for normal bone and tooth structure, and found especially in fish-liver oils, egg yolk, and milk or produced by activation (as by ultraviolet irradiation) of sterols: as
a
: calciferol
b
: cholecalciferol

called also sunshine vitamin

More from Merriam-Webster on vitamin D

Britannica.com: Encyclopedia article about vitamin D

Last Updated: - Updated example sentences
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