Plural of “cortex”

The plural of cortex is cortices.

Why

"Cortex" is Latin for bark or rind, the outer covering of a tree, and English borrowed it directly for anatomy and botany to describe an outer layer of tissue — the cerebral cortex, the adrenal cortex, a plant's root cortex. Because its use has stayed almost entirely within scientific and medical writing since it entered English in the 17th century, it retained the Latin third-declension plural "cortices" far more completely than the more everyday -ex words on this list.

"Cortexes" does appear occasionally in looser popular-science or journalistic writing, but style guides in medicine, neuroscience, and botany treat "cortices" as the standard and expected form, with "cortexes" reading as a noticeable departure from professional convention rather than a fully accepted equal alternative the way "vortexes" or "apexes" now are.

Usage note

In any scientific, medical, or academic writing, use "cortices." In general audience science journalism, either form may appear, but "cortices" still signals more careful, field-appropriate usage.

The word's most common modern use, "cerebral cortex," refers to the brain's outer layer of neural tissue responsible for higher cognitive functions; when discussing more than one region or more than one brain's cortex, "cortices" is the form used almost universally in neuroscience literature. Beyond the brain, "cortex" describes outer layers throughout biology — the adrenal cortex producing hormones, a plant stem's cortex beneath the epidermis, even a hair's outer cortex layer in cosmetic science — and in every one of these specialized fields, "cortices" remains the expected professional plural, showing how consistently this word has resisted regularization across disciplines that rarely otherwise overlap.

Common real mistakes

A frequent error is treating "cortices" as though it were singular, given how unfamiliar the Latin plural pattern feels to writers outside medicine and neuroscience; remember that "cortex" is singular and "cortices" is exclusively plural, just as with "vortex/vortices" and "index/indices."

The wider pattern

"Cortex" sits alongside "vortex" as one of the two words in this -ex family where the Latin plural remains genuinely dominant rather than merely accepted, largely because both words have stayed rooted in technical fields (fluid dynamics for "vortex," anatomy and botany for "cortex") that have historically preserved Latin scientific vocabulary more faithfully than everyday speech does. Brain imaging technology has made the cerebral cortex a household term over the past few decades, with popular science writing about neuroplasticity and cognition regularly discussing several cortical regions together, and even in that popularized register, "cortices" has remained the standard plural far more consistently than comparable popularized scientific terms.

Examples

• The scan showed unusual activity in both visual cortices.
• Researchers compared the cortices of several primate species.
• The adrenal cortices produce hormones essential to stress response.
• Botanists examined the root cortices for signs of fungal infection.
• Neurologists mapped the patient's motor cortices before the surgery.
• The study measured thickness across several regions of the cerebral cortices.
• Both cortices showed reduced activity during the deep sleep phase.
• The textbook diagrams the layers within the kidney's cortices.
• Scientists tracked how the cortices developed differently in each twin.
• Damage to both cortices affected the patient's memory in distinct ways.
• The dermatologist explained how UV damage affects the hair's outer cortices.
• Botanists compared root cortices across drought-resistant plant varieties.
• Surgeons carefully avoided both visual cortices during the delicate procedure.
• The textbook illustrates cross-sections through several plant stem cortices.
• Popular science books often describe how different cortices process sensory input.
• The study compared cortices across subjects with and without the condition.
• Surgeons mapped both cortices before planning the delicate operation.
• Researchers found measurable differences between the cortices of trained musicians and non-musicians.
• The study tracked how both cortices changed over years of training.
• Surgeons carefully mapped the cortices before the operation began.