Standard Lemma guide

isomer

noun · 3 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.

  • Received-Pronunciation: /ˈaɪ.sə.mə/
  • US: ī'səmər
  • US: /ˈaɪ.sə.mɚ/
  • US: Recorded audio is listed in the source snapshot.
  • Australia: Recorded audio is listed in the source snapshot.
  • CMU ARPABET: AY1 S AH0 M ER0 Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.

1

noun

Meaning 1

Any of two or more compounds with the same molecular formula but with different structure.

Definition source: English Wiktionary via Wiktextract

Usage: physical

Topics: chemistry, natural-sciences, physical-sciences

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

Any of two or more atomic nuclei with the same mass number and atomic number but with different radioactive properties.

Definition source: English Wiktionary via Wiktextract

Qualifier: nuclear physics

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

3

noun

Meaning 3

a compound that exists in forms having different arrangements of atoms but the same molecular weight

Definition source: Princeton WordNet 3.0

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

Broader terms: compound, chemical compound

History

Etymology

From iso- + -mer.

Across languages

Translations

41 source translations are retained for this English entry.

  • Catalan: isòmer — chemistry: compounds
  • Chinese Cantonese: 異構體 /异构体 (ji6 kau3 tai2, ji6 gau3 tai2) — chemistry: compounds
  • Chinese Mandarin: 異構體 /异构体 (yìgòutǐ) — chemistry: compounds
  • Chinese Mandarin: 同分異構體 /同分异构体 (tóngfēnyìgòutǐ) — chemistry: compounds
  • Czech: izomer — chemistry: compounds
  • Danish: isomeri — chemistry: compounds
  • Esperanto: izomero — chemistry: compounds
  • Finnish: isomeeri — chemistry: compounds
  • French: isomère — chemistry: compounds
  • Galician: isómero — chemistry: compounds
  • German: Isomer — chemistry: compounds
  • Greek: ισομερές (isomerés) — chemistry: compounds
  • Hindi: समावयव (samāvyav) — chemistry: compounds
  • Hungarian: izomer — chemistry: compounds
  • Ido: izomero — chemistry: compounds
  • Indonesian: isomer — chemistry: compounds
  • Irish: isiméir — chemistry: compounds
  • Italian: isomero — chemistry: compounds
  • Japanese: 異性体 (iseitai) — chemistry: compounds
  • Kazakh: изомер (izomer) — chemistry: compounds
  • Khmer: អ៊ីសូមែ (ʼiisoumɛɛ) — chemistry: compounds
  • Malay: isomer — chemistry: compounds
  • Māori: poinanaha — chemistry: compounds
  • Persian: ایزومر (izomer) — chemistry: compounds
  • Polish: izomer — chemistry: compounds
  • Portuguese: isômero — chemistry: compounds
  • Russian: изоме́р (izomér) — chemistry: compounds
  • Spanish: isómero — chemistry: compounds
  • Swedish: isomer — chemistry: compounds
  • Tagalog: kasanyo — chemistry: compounds
  • Turkish: izomer — chemistry: compounds
  • Yiddish: איסאָמער (isomer) — chemistry: compounds
  • Chinese Mandarin: 同核異能素 /同核异能素 (tónghéyìnéngsù) — physics: atomic nuclei
  • French: isomère — physics: atomic nuclei
  • German: Kernisomer — physics: atomic nuclei
  • Greek: ισομερές (isomerés) — physics: atomic nuclei
  • Irish: isiméir — physics: atomic nuclei
  • Italian: isomero — physics: atomic nuclei
  • Japanese: 異性核 (iseikaku) — physics: atomic nuclei
  • Polish: izomer — physics: atomic nuclei
  • Russian: изоме́р (izomér) — physics: atomic nuclei