regolith

/ˈɹɛɡəlɪθ/

//ˈɹɛɡəlɪθ// noun

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

"regolith" is a 8-letter English headword indexed on PlainSpell.

The verdict

“regolith” is uncommon English (frequency #78,070 among 3,094 “R” headwords), classed as a noun. The kind of spelling people second-guess.

#78,070
frequency rank, English
3,094
“R” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - The layer of loose rock, dust, sand, and soil, resting on the bedrock, that constitutes the surface layer of most dry land on Earth, the Moon, and other large solid aggregated celestial objects. Su...

Corpus desk

Index EN-regolith · regolith · English

regolith · rank #78,070 · 0 variants · 0 confusables

  • FREQ-RARE #78,070
  • LEN-LONG 8 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 3,094
  • PHOTO-FINISH regicide

Nearest frequency peer: regicide (-1 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 “regolith”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “regolith” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for regolith
PropertyValue
Headwordregolith
LanguageEnglish
Part of speechNoun
IPA/ˈɹɛɡəlɪθ/
Letters8
Frequency rank#78,070
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “regolith” in English

This scale runs from the tiny cluster of words that carry ordinary speech (left) to the long tail of words almost nobody reaches for (right).regolithfalls in this rarity band:

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

The axis is logarithmic, with each marked tick roughly ten times rarer than the last. Rare peers in the same band: “regicide” (#78,069), “renminbi” (#78,073), “rennet” (#78,074). Among 3,094 “R” headwords, “regolith” is #78,070. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

regolith is uncommon English at frequency #78,070 among 3,094 “R” headwords, classed as anoun, transcribed /ˈɹɛɡəlɪθ/. Rarity is why readers land here mid-draft. Gloss: "The layer of loose rock, dust, sand, and soil, resting on the bedrock, that constitutes the surface layer of most dry land on Earth, the Moon, and other large solid aggregated celestial objects. Su...".

regolith doesn't appear in our generated misspelling index, since its letter sequence doesn't invite the usual edit-distance slips. No confusable counterpart is on file for this word, since no other headword is close enough in sound or shape to pair with it.

Etymologically, the entry records: Irregular formation from Ancient Greek ῥῆγος (rhêgos, “rug, blanket”) + -lith (from λίθος (líthos, “stone”)). The correct English form is regolith, spelled R-E-G-O-L-I-T-H.

Definition

  1. 1
    The layer of loose rock, dust, sand, and soil, resting on the bedrock, that constitutes the surface layer of most dry land on Earth, the Moon, and other large solid aggregated celestial objects. Submarine regolith also exists.

Recorded use

Wiktionary examples

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

  1. The structures on the surface were gone from normal view, pulverized into regolith across a span of aeons.
  2. The soil sample, called LZS-1, is the latest in a list of lunar regolith simulants of varying quality that have been developed to help Nasa and other space agencies around the world prepare for missions to the Moon.

Etymology

Irregular formation from Ancient Greek ῥῆγος (rhêgos, “rug, blanket”) + -lith (from λίθος (líthos, “stone”)).

This word in other languages

regolito(Español)régolithe(Français)

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 "regolith"?
"regolith" is spelled R-E-G-O-L-I-T-H. The IPA pronunciation is /ˈɹɛɡəlɪθ/.
What does "regolith" mean?
As a noun, "regolith" means: The layer of loose rock, dust, sand, and soil, resting on the bedrock, that constitutes the surface layer of most dry land on Earth, the Moon, and other large solid aggregated celestial objects. Su...
How do you pronounce "regolith"?
The IPA (International Phonetic Alphabet) transcription for "regolith" is /ˈɹɛɡəlɪθ/. 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 "regolith"?
Irregular formation from Ancient Greek ῥῆγος (rhêgos, “rug, blanket”) + -lith (from λίθος (líthos, “stone”)). 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 "regolith", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 8 letters (nearest by frequency rank).

regicide#78,069renminbi#78,073recurved#78,064rootless#78,086

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

Source: FrequencyWords open word-frequency list