epoch

Pluralepochs

1. 1
   period in historynouncountable

   A particular period in history or in a person's life, especially one seen as notable or remarkable.

   The printing press opened a new epoch in the spread of ideas across Europe.

   She looked back on her years in Paris as the happiest epoch of her life.

   UsageOften a new epoch or the end of an epoch. Epoch-making means important enough to begin one.

   Similarera, age

2. 2
   geologynouncountable

   A unit of geologic time forming part of a period and divided into ages or sometimes subepochs, lasting anywhere from thousands to tens of millions of years.

   Mammoths roamed much of the Northern Hemisphere during the Pleistocene epoch.

   Geologists divide the Neogene period into two epochs, the Miocene and the Pliocene.

   UsagePut the name before epoch: the Pleistocene epoch, the Miocene epoch.

   Note

   In everyday English epoch, era, period and age can trade places; in geology each is a separate rung, and the order matters. Eras contain periods, periods contain epochs, and epochs contain ages, so the Pleistocene is an epoch, never an era. A name or a describing word comes first: the Pleistocene epoch, or the glacial epoch of Alfred Russel Wallace's Island Life. Source

   Checked 31 Oct 2026 · 4 facts

   • Geological eras contain periods, periods contain epochs, and epochs contain ages. bgs.ac.uk
   • The Pleistocene is classified as an epoch rather than an era. quaternary.stratigraphy.org
   • Alfred Russel Wallace wrote Island Life. wallace-online.org
   • Wallace uses the expression 'glacial epoch' in Island Life. wallace-online.org
3. 3
   zero pointnouncountable

   A specific instant chosen as the reference point, or zero, of a system for identifying moments in time.

   Unix time counts the seconds that have passed since the epoch, midnight UTC on January 1, 1970.

   GPS receivers count time in weeks and seconds from the GPS epoch, midnight on January 6, 1980.

   Note

   Choosing an epoch is what turns a count into a date, and systems disagree: Unix counts from 1970, some timestamps from 1601, .NET from the start of AD 1. Astronomers fix their own, such as J2000, noon on January 1, 2000. That is why the word usually travels with its system's name: the Unix epoch, the J2000 epoch. Source

   Checked 31 Oct 2026 · 5 facts

   • An epoch supplies the reference point for interpreting a time count. en.wikipedia.org
   • Unix time uses an epoch in 1970. en.wikipedia.org
   • Some timestamps count from 1601, including Windows FILETIME. learn.microsoft.com
   • .NET DateTime counts ticks from the beginning of AD 1. learn.microsoft.com
   • Astronomy uses J2000, corresponding to noon on January 1, 2000, in Terrestrial Time. aa.usno.navy.mil
4. 4
   training passnouncountable

   One complete pass of the whole training data set through an iterative machine learning algorithm.

   The model's accuracy stopped improving after about twenty epochs, so we halted training.

   Each epoch took nearly an hour on a single GPU.

   Note

   Training is counted in epochs because a model rarely learns enough from one pass. Each epoch is usually split into batches, and the model typically updates after every batch, so an epoch usually contains many steps or iterations. Too many epochs let a model memorize its training data, so training often stops once held-out results stop improving. Source

   Checked 31 Oct 2026 · 5 facts

   • Training typically requires multiple passes through the training data. developers.google.com
   • Epochs are commonly divided into batches, with a model update after each batch. keras.io
   • An epoch commonly contains many training iterations, but with full-batch training it contains just one iteration and one update. developers.google.com
   • Excessive training can cause overfitting to the training data. tensorflow.org
   • Training is often stopped when performance on held-out validation data stops improving. keras.io

Showing meanings only. Show all 6