SFO

name

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

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

The verdict

“SFO” sits in 20 confusable pairs (corpus #42,889) as a proper noun. The look-alike neighbours are the real trap.

#42,889
frequency rank, English
54,294
“S” headwords
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Initialism of Serious Fraud Office.

Visual similarity to commonly confused words

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

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

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

Key facts for SFO
PropertyValue
HeadwordSFO
LanguageEnglish
Part of speechProper noun
Letters3
Frequency rank#42,889
Misspellings tracked0
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “SFO” 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). SFO lands here:

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

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

Easy to mix with look-alikes

The spelling risk for SFO is neighbouring look-alikes ("so", "SI", …), not just typos; it is aproper noun. Frequency #42,889 among 54,294 “S” headwords. 2 recorded senses keep meaning in play.

SFO doesn't appear in our generated misspelling index, a sign its spelling follows regular English conventions. It also participates in 20 confusable-pair relationships, "so", "SI", "SS", and more, a pairing that trips writers up because the two words share enough sound or shape to blur together.

Our source data has no etymology on file for this entry, so spelling patterns must be inferred from the word's phoneme-to-grapheme mapping rather than from a documented borrowing chain. The correct English form is SFO, spelled S-F-O.

Definition

  1. 1
    Initialism of Serious Fraud Office.
  2. 2
    Abbreviation of San Francisco International Airport.

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 "SFO"?
"SFO" is spelled S-F-O.
What does "SFO" mean?
As a proper noun, "SFO" means: Initialism of Serious Fraud Office.
What words are commonly confused with "SFO"?
"SFO" is commonly confused with "so", "SI", "SS". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
What language does "SFO" come from?
"SFO" is a English word. PlainSpell's reference spans five languages -- English, Spanish, Portuguese, French, and German -- with definitions, pronunciations, and spelling data for each.
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 “SFO”

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

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

Words at a similar English frequency

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