sei

/seɪ/

//seɪ// noun

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

"sei" is a 3-letter English headword indexed on PlainSpell.

The verdict

“sei” sits in 20 confusable pairs (corpus #34,681) as a noun. The look-alike neighbours are the real trap.

#34,681
frequency rank, English
6,566
“S” headwords
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - A sei whale.

Corpus desk

Index EN-sei · sei · English

sei · rank #34,681 · 0 variants · 20 confusables

  • FREQ-MID #34,681
  • LEN-MID 3 letters
  • VOW-2 2 vowels
  • CONFUS-HIGH 20 pairs
  • VAR-0 0 variants
  • BOOK-DENSE 6,566
  • PHOTO-FINISH shrieking

Nearest frequency peer: shrieking (+2 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.

Frequency neighbours of confusable “sei”

Peers at similar corpus weight, separate from look-alike pairs below

corpus weight

What this shows Bars place “sei” against nearest ranked English headwords, not a reprint of the confusable-pair desk.

Source FrequencyWords open word-frequency list As of September 3, 2026

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

sei vs so
33% similar
sei vs SI
0% similar
sei vs SS
0% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for sei
PropertyValue
Headwordsei
LanguageEnglish
Part of speechNoun
IPA/seɪ/
Letters3
Frequency rank#34,681
Misspellings tracked0
Confusable pairs20
SourceWiktionary (kaikki.org)

Corpus rank beside confusables of “sei”

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right).seilands here:

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

The axis is logarithmic, with each marked tick roughly ten times rarer than the last. Same rarity band neighbours include “shrieking” (#34,683), “Schuyler” (#34,678), “Sauron” (#34,677). Among 6,566 “S” headwords, “sei” is #34,681. Source: FrequencyWords open word-frequency list.

Easy to mix with look-alikes

The spelling risk for sei is neighbouring look-alikes ("so", "SI", …), not just typos; it is anoun pronounced /seɪ/. Frequency #34,681 among 6,566 “S” headwords. Gloss: "A sei whale.".

No generated misspelling entries exist for sei in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. It also participates in 20 confusable-pair relationships, "so", "SI", "SS", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: From sei whale, from Norwegian seihval, seikval, from sei (“pollock”) + hval (“whale”). Doublet of saithe. The correct English form is sei, spelled S-E-I.

Definition

  1. 1
    A sei whale.

Recorded use

Wiktionary example

These source excerpts show how sei appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Seis also feed by engulfing small schooling fish.

Etymology

From sei whale, from Norwegian seihval, seikval, from sei (“pollock”) + hval (“whale”). Doublet of saithe.

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 "sei"?
"sei" is spelled S-E-I. The IPA pronunciation is /seɪ/.
What does "sei" mean?
As a noun, "sei" means: A sei whale.
What words are commonly confused with "sei"?
"sei" is commonly confused with "so", "SI", "SS". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "sei"?
The IPA (International Phonetic Alphabet) transcription for "sei" is /seɪ/. 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 "sei"?
From sei whale, from Norwegian seihval, seikval, from sei (“pollock”) + hval (“whale”). Doublet of saithe. 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 "sei", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 3 letters (nearest by frequency rank).

Siu#34,689soi#34,694PRS#34,651urs#34,739

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

Source: FrequencyWords open word-frequency list