ISI

noun

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

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

The verdict

“ISI” is a moderately-common English word, ranked #25,430 in English word frequency and used as a noun.

#25,430
frequency rank, English
3
letters
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Abbreviation of intersymbol interference.

Visual similarity to commonly confused words

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

ISI vs it
0% similar
ISI vs IV
33% similar
ISI vs iz
0% similar

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

Key facts for ISI
PropertyValue
HeadwordISI
LanguageEnglish
Part of speechNoun
Letters3
Frequency rank#25,430
Misspellings tracked0
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “ISI” sits in English frequency

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

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

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for ISI is 3 letters long, classified as a noun. Corpus data places it at rank #25,430 in overall English word frequency, marking it as uncommon enough that many writers pause before typing it. Wiktionary records 3 distinct senses for this headword, so context determines which meaning a reader should apply.

Zero misspellings are on record for ISI in our index, which points to an orthography that plays by predictable English rules. It also participates in 20 confusable-pair relationships, "it", "IV", "iz", and more, where similar look or sound leads writers to substitute one word for another in context.

No borrowing history is documented for this entry, so its spelling pattern is best understood through pronunciation rather than a traceable origin. The correct English form is ISI, spelled I-S-I.

Definition

  1. 1
    Abbreviation of intersymbol interference.
  2. 2
    Initialism of international sensitivity index.
  3. 3
    Initialism of import substitution industrialization.

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 "ISI"?
"ISI" is spelled I-S-I.
What does "ISI" mean?
As a noun, "ISI" means: Abbreviation of intersymbol interference.
What words are commonly confused with "ISI"?
"ISI" is commonly confused with "it", "IV", "iz". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
What language does "ISI" come from?
"ISI" is a English word. You can look up definitions, pronunciations, and spelling data for this and other words across English, Spanish, Portuguese, French, and German on PlainSpell.
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.

Using “ISI”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is I-S-I - every other letter order is a misspelling in standard orthography.
  • Don't mix it up with “it” - see the side-by-side comparison. ISI vs it
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

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

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list