Plural of “plateau”

The plural of plateau is plateaus (some dictionaries also accept plateaux).

Why

"Plateau" comes from French "plateau," a diminutive of "plat," meaning flat — literally a "little flat thing," originally describing a flat serving dish before geography borrowed it for a flat, elevated landform. Its figurative sense (a period where progress levels off, as in weight loss or skill development) developed later, entirely within English, once the geographic meaning was well established.

"Plateaus" has become the dominant plural by a wide margin in both the geographic and figurative senses, likely because the figurative use in particular — describing a person's fitness or a company's sales hitting a "plateau" — happens overwhelmingly in casual, non-specialist writing where the French plural has essentially no foothold left.

Usage note

"Plateaus" is the safe, standard choice in virtually every context today; "plateaux" survives mainly in specifically geological or geographic academic writing and reads as noticeably more formal or old-fashioned elsewhere.

The figurative sense — reaching a plateau in progress — is now arguably more common in everyday English than the literal landform sense, and this figurative usage has never shown any real attraction to the French plural spelling, reinforcing how thoroughly "plateaus" has taken over outside specialist geography. Geologists distinguish between plateaus formed by volcanic activity, by erosion of surrounding land, and by tectonic uplift, and technical geology writing uses "plateaus" for all three formation types without any special terminology distinguishing them at the plural level — a further sign of how completely the regularized plural has taken over even in scientific contexts for this particular word.

Common real mistakes

Writers occasionally drop the -u before adding -s, misspelling the plural as "platoes" or "plateaus" without realizing the word retains its full French spelling before the English plural ending — the correct base is "plateau-" plus "-s," not any shortened form.

The wider pattern

"Plateau" is the furthest along the regularization path among these French -eau nouns — more so than "bureau" or "chateau" — likely because its figurative extension into everyday, non-French-flavored contexts (fitness, sales, learning curves) accelerated its shift toward the ordinary English plural. The Tibetan Plateau, sometimes called the "Roof of the World," is the largest and highest plateau on Earth, and geography textbooks comparing it to other major plateaus worldwide — the Colorado Plateau, the Deccan Plateau — use "plateaus" without any hesitation, reflecting the word's complete regularization even in serious academic geography.

Examples

• The hikers crossed two plateaus before reaching the final summit.
• Her weight loss hit a plateau after the first few months.
• Several plateaus in the region were formed by ancient volcanic activity.
• Sales reached a plateau that lasted nearly a full year.
• Geologists mapped the plateaus stretching across the high desert.
• The runner's times reached a plateau despite months of training.
• Two distinct plateaus were visible from the plane window.
• Economists noted plateaus in wage growth across several industries.
• The trail wound through a series of grassy plateaus.
• Both plateaus offered sweeping views of the valley below.
• The expedition crossed three high-altitude plateaus before reaching base camp.
• Her recovery hit several plateaus before showing real improvement.
• The region's plateaus are known for their unusually fertile soil.
• Two adjoining plateaus were separated by a narrow, steep canyon.
• Geography textbooks compare the world's largest plateaus by elevation and area.
• Her fitness plateaus eventually broke once she changed her training routine.
• The expedition surveyed two remote plateaus never previously mapped in detail.
• Economic growth hit plateaus in several regions during the recession.
• The climbers rested on one of several plateaus along the ascent.
• Sales growth reached a plateau before picking up again the following quarter.
• The survey team spent weeks mapping plateaus across the remote interior.
• His progress reached a plateau that lasted the better part of a year.