periostracum
noun
periostracum is spelled P-E-R-I-O-S-T-R-A-C-U-M: 12 letters. It appears about once in every 41 million words in written English, the 196,618th most frequent word form (wordfreq, 2021 data). As a noun, periostracum means “The proteinaceous outer sheath of many molluscan shells” (English Wiktionary, September 2026). The plural of periostracum is periostraca or periostracums.
How many letters and syllables are in periostracum?
| Letters | 12: P-E-R-I-O-S-T-R-A-C-U-M |
|---|---|
| In writing | about once in every 41 million words; the 196,618th most frequent word form |
| Wrong spellings searched | none measured in search |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How common is periostracum?
Periostracum appears about once in every 41 million words in written English, the 196,618th most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Forms of periostracum
- periostraca plural
- periostracums plural
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does periostracum mean?
The meanings the English Wiktionary records, quoted as written there (source below).
noun
- 1
The proteinaceous outer sheath of many molluscan shells.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Where does periostracum come from?
Literally "surrounding shell", from peri- + ostracum.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).