femtosecond
"femtosecond" is a 11-letter English headword indexed on PlainSpell.
The verdict
“femtosecond” is uncommon English (frequency #84,242 among 2,507 “F” headwords), classed as a noun. The kind of spelling people second-guess.
- #84,242
- frequency rank, English
- 2,507
- “F” headwords
According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - An SI unit of time equal to 10⁻¹⁵ seconds. Symbol: fs
Corpus desk
Index EN-femtosecond · femtosecond · English
femtosecond · rank #84,242 · 0 variants · 0 confusables
- FREQ-RARE #84,242
- LEN-MEGA 11 letters
- VOW-4 4 vowels
- CONFUS-0 No pairs
- VAR-0 0 variants
- BOOK-MID 2,507
- PHOTO-FINISH fetter
Nearest frequency peer: fetter (+3 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 “femtosecond”
Sparse band: bars invert rank so rarer forms read shorter
- extensional
extensional
15,768 corpus weight
- FATT
FATT
15,764 corpus weight
- faubourg
faubourg
15,763 corpus weight
- femtosecond
femtosecond
15,759 corpus weight
- fetter
fetter
15,756 corpus weight
- Firmin
Firmin
15,750 corpus weight
What this shows Long-tail view: where “femtosecond” sits against similarly uncommon English ranks.
| Property | Value |
|---|---|
| Headword | femtosecond |
| Language | English |
| Part of speech | Noun |
| Letters | 11 |
| Frequency rank | #84,242 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Long-tail rank of “femtosecond” in English
Rare enough to double-check
femtosecond is uncommon English at frequency #84,242 among 2,507 “F” headwords, classed as anoun. Rarity is why readers land here mid-draft. Gloss: "An SI unit of time equal to 10⁻¹⁵ seconds. Symbol: fs".
Zero misspellings are on record for femtosecond in our index, since its letter pattern doesn't lend itself to common typo substitutions. We don't track a confusable pairing for this entry, which tends to mean the word is visually distinctive enough to stand on its own.
Etymologically, the entry records: From femto- + second. The correct English form is femtosecond, spelled F-E-M-T-O-S-E-C-O-N-D.
Definition
- 1An SI unit of time equal to 10⁻¹⁵ seconds. Symbol: fs
Recorded use
Wiktionary examplesThese source excerpts show how femtosecond appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.
Holonyms: picosecond < nanosecond < microsecond < millisecond < centisecond < decisecond < second < decasecond < minute < hectosecond < kilosecond < hour < day < week < megasecond < fortnight < month < year < gigasecond < century < kiloannum, kiloyear, millennium < terasecond < mega-annum, megayear < petasecond < giga-annum, gigayear < exasecond < zettase…
Meronyms: quectosecond < rontosecond < yoctosecond < zeptosecond < attosecond
Etymology
From femto- + second.
This word in other languages
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
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Similar English words by spelling shape
Same letter count and similar misspelling depth for "femtosecond", not the corpus desk frequency band.
Same letter count
Frequency-ranked English headwords with 11 letters (nearest by frequency rank).