Standard Lemma guide

E=mc2

noun · 2 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: /ˈiː ˌiːkwəlz ɛm siː ˈskwɛːd/
  • Canada, General-American: /ˈi ˌikwəlz ɛm si ˈskwɛɹd/
  • General-American: Recorded audio is listed in the source snapshot.
  • rhymes with -ɛə(ɹ)d

1

noun

Meaning 1

A formulation or realization that captures a profound thought in simple terms.

Definition source: English Wiktionary via Wiktextract

Usage: idiomatic, informal, uncountable

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

Used other than figuratively or idiomatically: E = mc2: energy equals mass times the speed of light squared.

Definition source: English Wiktionary via Wiktextract

Usage: uncountable

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

History

Etymology

After the formula of mass–energy equivalence, an important principle discovered by the German-born theoretical physicist Albert Einstein (1879–1955). The formula entered the popular consciousness after it was included in the opening pages of the Smyth Report (1945), a widely read document that explained the United States’ nuclear weapons program to the public for the first time. Its appearance alongside a portrait of the (already well known) Einstein on a Time magazine cover the following year consolidated its fame.