# epoch

/ˈɛpək/ (US) · /ˈɛpɒk/ (UK)

Source: https://englishreference.com/word/epoch
Updated: 2026-08-27

## Senses

### 1. historical period

noun · CEFR C1 · Academic · Literary

a long period of time in history that is important because of specific events or changes.

For teachers: a distinct period in history or a person's life, typically marked by notable events or a particular state of affairs.

- The invention of the steam engine marked a new epoch in industrial history.
- Historians often argue that the fall of the Berlin Wall signaled the end of a geopolitical epoch defined by the Cold War.

### 2. geological time

noun · CEFR C2 · Technical

a unit of time used by scientists to describe millions of years in Earth's history.

For teachers: a geochronologic unit of time, typically lasting millions of years, representing a subdivision of a period.

- We are currently living in the Holocene epoch, which began after the last ice age.
- The transition between the Eocene and Oligocene epochs is marked by significant global cooling and changes in marine life.

### 3. computing reference point

noun · CEFR C2 · Technical

the exact date and time that a computer system uses to start counting time.

For teachers: a fixed point in time used as a reference from which time is measured in a computing system.

- The Unix epoch began at midnight on January 1, 1970.
- The system clock calculates the current time by counting the number of seconds elapsed since the designated epoch.

Usage: Often used with 'the' as a proper noun in specific contexts like 'the Unix epoch'.

### 4. machine learning cycle

noun · CEFR C2 · Technical

one full cycle of training an AI using all the available data.

For teachers: one complete pass of the entire training dataset through a machine learning algorithm.

- The model's accuracy improved significantly after the tenth epoch of training.
- Training was halted after fifty epochs to prevent the neural network from overfitting the training data.

### 5. to segment data

verb · CEFR C2 · Technical

to divide a long recording of data into smaller pieces based on time.

For teachers: to segment continuous data, such as an EEG recording, into specific time-locked windows for analysis.

- The researcher had to epoch the brainwave data to analyze the response to each sound.
- The raw signal was epoched into two-second intervals relative to the onset of the visual stimulus.

## Examples

- The invention of the steam engine marked a new epoch in history.
- Geologists study different layers of rock to determine when one epoch ended and another began.
- The fall of the Berlin Wall is often cited as the event that closed one political epoch and inaugurated a period of rapid globalization.

---

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.