sesquicentennial

/ˌsɛskwɪsɛnˈtɛni.əl/

//ˌsɛskwɪsɛnˈtɛni.əl// adj

By · According to Wiktionary data (CC BY-SA) ·

"sesquicentennial" is a 16-letter English headword indexed on PlainSpell.

The verdict

“sesquicentennial” is uncommon English (frequency #95,400 among 6,566 “S” headwords), classed as an adjective. The kind of spelling people second-guess.

#95,400
frequency rank, English
6,566
“S” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Occurring every 150 years.

Corpus desk

Index EN-sesquicentennial · sesquicentennial · English

sesquicentennial · rank #95,400 · 0 variants · 0 confusables

  • FREQ-RARE #95,400
  • LEN-MEGA 16 letters
  • VOW-7 7 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-DENSE 6,566
  • PHOTO-FINISH Sers

Nearest frequency peer: Sers (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Long-tail ranks near “sesquicentennial”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “sesquicentennial” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for sesquicentennial
PropertyValue
Headwordsesquicentennial
LanguageEnglish
Part of speechAdjective
IPA/ˌsɛskwɪsɛnˈtɛni.əl/
Letters16
Frequency rank#95,400
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “sesquicentennial” in English

This scale runs from the tiny cluster of words that carry ordinary speech (left) to the long tail of words almost nobody reaches for (right).sesquicentennialfalls in this rarity band:

#1#100#1K#10K#100K
← used constantlyrarely used →

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Rare peers in the same band: “Sers” (#95,399), “seventieth” (#95,401), “serotonergic” (#95,398). Among 6,566 “S” headwords, “sesquicentennial” is #95,400. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

sesquicentennial is uncommon English at frequency #95,400 among 6,566 “S” headwords, classed as anadjective, transcribed /ˌsɛskwɪsɛnˈtɛni.əl/. Rarity is why readers land here mid-draft. 2 senses are on record.

sesquicentennial has no tracked misspelling variants, suggesting the orthography follows predictable English patterns. Our confusable-pair dataset has no match for it, which tends to mean the word is visually distinctive enough to stand on its own.

Etymologically, the entry records: From sesqui- (“one-and-a-half”) + centennial (“of 100 years”). By surface analysis, sesqui- + cent- + -ennial. The correct English form is sesquicentennial, spelled S-E-S-Q-U-I-C-E-N-T-E-N-N-I-A-L.

Definition

  1. 1
    Occurring every 150 years.
  2. 2
    Of, or relating to a sesquicentenary.

Etymology

From sesqui- (“one-and-a-half”) + centennial (“of 100 years”). By surface analysis, sesqui- + cent- + -ennial.

This word in other languages

sesquicentenário(Português)

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "sesquicentennial"?
"sesquicentennial" is spelled S-E-S-Q-U-I-C-E-N-T-E-N-N-I-A-L. The IPA pronunciation is /ˌsɛskwɪsɛnˈtɛni.əl/.
What does "sesquicentennial" mean?
As an adjective, "sesquicentennial" means: Occurring every 150 years.
How do you pronounce "sesquicentennial"?
The IPA (International Phonetic Alphabet) transcription for "sesquicentennial" is /ˌsɛskwɪsɛnˈtɛni.əl/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "sesquicentennial"?
From sesqui- (“one-and-a-half”) + centennial (“of 100 years”). By surface analysis, sesqui- + cent- + -ennial. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "sesquicentennial", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 16 letters (nearest by frequency rank).

electromagnetics#96,986organizationally#92,955pharmacodynamics#98,564phylogenetically#98,570

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list