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Noun, pl.fontanelles

Also spelled as fontanel.

1. Any membranous gap between the bones of the cranium in an infant or fetus. (

2. A soft membraneous spot on the head of a baby due to incomplete fusion of the cranial bones. (

3. An anatomical feature on an infant’s skull comprised by any of the soft membranous gaps between the incompletely formed cranial bones of a foetus or an infant. Fontanelles allow for rapid stretching and deformation of the cranium as the brain expands faster than the surrounding bone can grow. (

Word origin: From French fontanelle (16c.), from Old French fontenele “small source, fountain, spring; fontanelle,” diminutive of fontaine “spring” (see fountain),

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