Latin phrase meaning 'the end before which' - the date before which a stratum, feature, or artifact must have been deposited. The term is used either to define a relative chronological date for artifacts or provide fixed points in a site's stratigraphy. If a deposit can be securely dated by material found in it - for example, coins dating to the 2nd century AD found above a layer would provide that deposit with a terminus ante quem of the 2nd century AD. In some circumstances, such a 'date' may be combined with a terminus post quem from an earlier phase to produce a date range for the intervening deposit. This type of dating is used to show that something cannot be later than, or earlier than, something else.