isomer

/ˈaɪ.sə.mə/

//ˈaɪ.sə.mə// noun

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

"isomer" is a 6-letter English headword indexed on PlainSpell.

The verdict

“isomer” is uncommon English (frequency #55,520 among 2,140 “I” headwords), classed as a noun. The kind of spelling people second-guess.

#55,520
frequency rank, English
2,140
“I” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Any of two or more compounds with the same molecular formula but with different structure.

Corpus desk

Index EN-isomer · isomer · English

isomer · rank #55,520 · 0 variants · 0 confusables

  • FREQ-RARE #55,520
  • LEN-LONG 6 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 2,140
  • PHOTO-FINISH inundation

Nearest frequency peer: inundation (-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 “isomer”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

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

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for isomer
PropertyValue
Headwordisomer
LanguageEnglish
Part of speechNoun
IPA/ˈaɪ.sə.mə/
Letters6
Frequency rank#55,520
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “isomer” 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).isomerfalls in this rarity band:

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

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Rare peers in the same band: “inundation” (#55,519), “Italiana” (#55,521), “Iyengar” (#55,522). Among 2,140 “I” headwords, “isomer” is #55,520. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

isomer is uncommon English at frequency #55,520 among 2,140 “I” headwords, classed as anoun, transcribed /ˈaɪ.sə.mə/. Rarity is why readers land here mid-draft. 2 senses are on record.

Zero misspellings are on record for isomer in our index, suggesting the orthography follows predictable English patterns. No close-neighbour confusable shows up for this headword in our dataset, suggesting its spelling stands apart enough that readers rarely confuse it with something else.

Etymologically, the entry records: From iso- + -mer. The correct English form is isomer, spelled I-S-O-M-E-R.

Definition

  1. 1
    Any of two or more compounds with the same molecular formula but with different structure.
  2. 2
    Any of two or more atomic nuclei with the same mass number and atomic number but with different radioactive properties.

Etymology

From iso- + -mer.

Synonyms

nuclear isomer

This word in other languages

isómero(Español)isomère(Français)Isomer(Deutsch)isômero(Português)

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 "isomer"?
"isomer" is spelled I-S-O-M-E-R. The IPA pronunciation is /ˈaɪ.sə.mə/.
What does "isomer" mean?
As a noun, "isomer" means: Any of two or more compounds with the same molecular formula but with different structure.
How do you pronounce "isomer"?
The IPA (International Phonetic Alphabet) transcription for "isomer" is /ˈaɪ.sə.mə/. 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 "isomer"?
From iso- + -mer. 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 "isomer", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 6 letters (nearest by frequency rank).

Kirwan#55,536Kokomo#55,537Hoxton#55,498horsey#55,497

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

Source: FrequencyWords open word-frequency list