Smooth, Smoothe, or Smoothen: Clearing Up the Grammar Difference

“Smooth,” “smoothe,” and “smoothen” appear to serve the same purpose, yet only one is universally accepted. This article dissects each form, shows where they diverge, and gives you practical rules for choosing correctly.

By the end, you’ll know when to keep “smooth” as an adjective, when “smoothe” is a dated variant, and when “smoothen” might slip past unnoticed in technical jargon.

Etymology: Where Each Form Came From

“Smooth” traces back to Old English smōþ, already carrying the sense of even and sleek. The spelling stabilized by the 17th century, locking in the modern six-letter form.

“Smoothe” is a Middle English spelling variant that lingered into early print culture. Chaucer used it, and so did Shakespeare on occasion, but printers dropped the final “e” by 1700 to match Latin-based orthographic reforms.

“Smoothen” arose in the 16th century through the productive English habit of adding the ‑en suffix to adjectives to form verbs. “Heighten,” “widen,” and “redden” followed the same pattern, giving “smoothen” a logical birth but a limited lifespan in everyday speech.

Modern Standard Usage: Which One Wins

In every contemporary style guide, “smooth” is the default adjective and the only accepted verb form. “Smoothe” is labeled archaic, and “smoothen” is tagged as nonstandard or specialized.

Corpus data from the Corpus of Contemporary American English shows “smooth the surface” outnumbering “smoothen the surface” by roughly 200:1. British National Corpus ratios are similar, confirming the preference on both sides of the Atlantic.

If you are writing for general audiences, use “smooth” as both adjective and verb to remain invisible to editors and proofreading software alike.

“Smoothe” in Historical Texts and Poetry

Encountering “smoothe” in older literature is common, so understanding context prevents misreading. Spenser’s Faerie Queene reads, “She with her beautie would the world bethrall, And make his rudenesse smoothe,” where the archaic spelling signals poetic diction.

Modern reprints often normalize the spelling to “smooth” in footnotes or silently in the main text. When quoting original sources, retain “smoothe” and add a sic if editorial precision is required.

Avoid reviving “smoothe” in new creative writing unless you are deliberately invoking historical flavor, and even then, use it sparingly to prevent distraction.

“Smoothen” in Technical and Scientific Registers

Specialized fields occasionally prefer “smoothen” to avoid ambiguity with the adjective “smooth.” In signal processing papers, you might read, “We smoothen the curve to reduce noise,” where the verb is clearly marked.

Data science libraries such as R’s `smoothen()` function and Python’s deprecated `smoothen` parameter keep the term alive within code comments and documentation. Outside these contexts, readers perceive it as stiff or overly technical.

Reserve “smoothen” for academic or technical writing when a precise, jargon-specific verb is necessary, and pair it with a parenthetical note or glossary entry if your audience is mixed.

Common Grammar Mistakes and How to Fix Them

Writers sometimes default to “smoothen” because it sounds parallel to “straighten” or “flatten,” yet that parallelism does not extend to standard English. Replace “smoothen” with “smooth” in everyday prose: change “He smoothens the edges” to “He smooths the edges.”

Another slip is using “smoothe” as a past-tense form: “She smoothe the table yesterday” is incorrect. The past tense of the standard verb is “smoothed,” never “smoothe.”

To self-check, run a find-and-replace pass for “smoothe” and “smoothen” in your draft, substituting “smooth” or “smoothed” as appropriate. Most grammar checkers flag these variants automatically, so enable style suggestions in your editor.

Practical Tips for Consistency in Editing

Create a custom style sheet that lists preferred forms; include “smooth (v), smooth (adj), smoothed (past), smoothing (progressive).” Distribute this sheet to collaborators to prevent drift.

Use regex search in code editors or word processors to isolate nonstandard variants. The pattern `b[sm|SM]oothe[n]?b` highlights every stray instance instantly.

When editing others’ work, leave marginal comments explaining the change: “Updated to standard verb form for clarity.” This educates writers and reduces repeat corrections.

Regional Variations and Dialectal Surprises

In Indian English, “smoothen” enjoys wider circulation in newspapers and corporate reports, influenced by similar formations like “focussed” and “utilise.” A 2020 Times of India headline reads, “The board plans to smoothen the merger process,” sounding natural to local readers.

Singaporean English follows a similar pattern, with government white papers employing “smoothen” in formal contexts. Recognize this when editing international documents; imposing American or British norms can inadvertently erase regional identity.

If you are writing for a global platform, flag the variant in a brief note: “This article uses international English spelling and grammar conventions.” Readers then expect occasional deviations like “smoothen.”

SEO Impact of Keyword Choice

Search engines treat “smoothen” as a low-volume variant, receiving roughly 2,400 global monthly searches compared to 90,000 for “smooth.” Targeting the niche term can yield quick ranking wins if content depth is high.

Integrate both forms naturally: “To smooth the workflow, we first smoothen the data pipeline.” This satisfies keyword diversity without stuffing, and the parenthetical clarification addresses both audiences.

Use structured data markup to signal linguistic variants. A JSON-LD glossary entry for “smoothen” can capture long-tail traffic while the main page remains optimized for “smooth.”

Actionable Checklist for Writers and Editors

1. Run a global search for “smoothe” and replace with “smooth” unless quoting historical text. 2. Replace every “smoothen” with “smooth” in general prose; retain it only in technical sections with clear context. 3. Add a style-guide entry defining acceptable contexts for each form.

4. When quoting pre-1700 sources, preserve original spelling and add [sic] only if ambiguity arises. 5. Export a custom dictionary file from your editor so future projects inherit the same preferences automatically.

6. Schedule a quarterly audit of published content to catch drift, especially after team changes or CMS migrations. Consistency compounds trust with readers and search engines alike.