stoma

American  

[stoh-muh] / ˈstoʊ mə /

noun

plural

stomata, stomas

1. Botany. Also any of various small apertures, especially one of the minute orifices or slits in the epidermis of leaves, stems, etc., through which gases are exchanged.

2. Zoology. a mouth or ingestive opening, especially when in the form of a small or simple aperture.

3. Medicine/Medical. an artificial opening between two hollow organs or between one hollow organ and the outside of the body, constructed to permit the passage of body fluids or waste products.

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stoma British  

/ ˈstəʊmə /

noun

1. botany an epidermal pore, present in large numbers in plant leaves, that controls the passage of gases into and out of a plant

2. zoology anatomy a mouth or mouthlike part

3. surgery an artificial opening made in a tubular organ, esp the colon or ileum See colostomy ileostomy

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stoma Scientific  

/ stō′mə /

plural

stomata

1. Botany One of the tiny openings in the epidermis of a plant, through which gases and water vapor pass. Stomata permit the absorption of carbon dioxide necessary for photosynthesis from the air, as well as the removal of excess oxygen. Stomata occur on all living plant parts that have contact with the air; they are especially abundant on leaves. A single leaf may have many thousands of stomata. Each stoma is generally between 10 to 30 microns in length and is surrounded by a pair of crescent-shaped cells, called guard cells. The guard cells can change shape and close the stoma in order to prevent the loss of water vapor.

2. Botany See Note at transpiration

3. Zoology A mouthlike opening, such as the oral cavity of a nematode.

4. Medicine A temporary or permanent opening in a body surface, especially the abdomen or throat, that is created by a surgical procedure, such as a colostomy or tracheostomy.

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Other Word Forms

• stomal adjective

Etymology

Origin of stoma

First recorded in 1675–85; from New Latin, from Greek stóma “mouth”

Explanation

In humans, a stoma is any opening or hole in the body. In plants, it's an opening that acts as a sort of mouth, allowing gas exchange. Stoma is a Greek word that means "mouth," and your mouth is indeed one kind of stoma, or natural opening in your body. Ears and nostrils are also stomas, as are holes created through surgery. An operation to help a patient breathe might create a stoma in their neck, for example. You can only see tiny plant stomas through a microscope; these small openings allow plants to take in the carbon dioxide they need for photosynthesis.

Example Sentences

She said: "Seeing stoma bags that are glittery and frilly it shows people that we're not just patients we're actually people."

From BBC • Mar. 24, 2026

"I just changed my stoma bag in my tent most of the time, just because I know who's been in there, and it feels like the cleanest place," she says.

From BBC • Jun. 26, 2025

The stoma, a small hole in her abdomen, removes the waste from her body into the fitted bag, which Lucy has to regularly empty.

From BBC • Jun. 26, 2025

But she has one other consideration - packing the essentials for her stoma bag.

From BBC • Jun. 26, 2025

Each of these openings is called a stoma.

From Outlines of Lessons in Botany, Part I; from Seed to Leaf by Newell, Jane H.