# FOE

/ˈfoʊ/ (US) · /fˈəʊ/ (UK)

Source: https://englishreference.com/word/foe
Updated: 2026-08-08

## Senses

### 1. an enemy

noun · CEFR B2 · Literary

an enemy or someone you are fighting against.

For teachers: an adversary or opponent in a conflict or struggle.

- In the story, the brave knight finally defeated his old foe.
- The two nations, once close allies, became bitter foes after the border dispute escalated into open conflict.

### 3. unit of energy

noun · CEFR C2 · Technical

a very large unit of energy used by scientists to measure things like exploding stars.

For teachers: a unit of energy equal to 10 to the power of 44 joules, typically used in astrophysics to measure the energy release of supernovae.

- The scientist explained that the supernova released several FOE of energy.
- Calculating the total kinetic energy of the stellar explosion required the use of FOE as a standard unit of measurement.

## Examples

- The knight faced his foe on the battlefield.
- In the final chapter of the novel, the hero must decide whether to forgive his oldest foe or seek revenge.
- The treaty was designed to transform a former foe into a strategic ally, though decades of mutual suspicion made the diplomatic transition exceptionally fragile.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.