speed of light
"speed-of-light" is a 12-letter English headword indexed on PlainSpell.
The verdict
“speed of light” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 14
- letters
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The speed of electromagnetic radiation, which in a perfect vacuum is equivalent to 299,792,458 metres per second.
| Property | Value |
|---|---|
| Headword | speed of light |
| Language | English |
| Part of speech | Noun |
| Letters | 14 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “speed of light” sits in English frequency
Rare enough to double-check
speed of light is uncommon English outside the top frequency list, classed as anoun. Rarity is why readers land here mid-draft. 3 senses are on record.
Zero misspellings are on record for speed of light in our index, suggesting the orthography follows predictable English patterns. This headword has no recorded confusable partner, since nothing in our dataset looks or sounds close enough to cause mix-ups.
No explicit etymology string is stored for this entry, so its spelling is best read as a straightforward mapping from sound to letter. The correct English form is speed of light, spelled S-P-E-E-D- -O-F- -L-I-G-H-T.
Definition
- 1The speed of electromagnetic radiation, which in a perfect vacuum is equivalent to 299,792,458 metres per second.
- 2A very rapid speed.
- 3A rate of travel of a signal equal to one cell per generation, the fastest possible speed in the Moore and von Neumann neighborhoods.
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). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “speed of light”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is S-P-E-E-D- -O-F- -L-I-G-H-T - every other letter order is a misspelling in standard orthography.
- 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.