The Hebrew verb nacham (H5162) carries two primary meanings: to comfort, console, or bring relief — and to repent, relent, or change one's mind. Both senses share the root idea of breathing deeply in response to a situation.
Nacham holds one of Scripture's greatest tensions: God both 'relents' from judgment and 'does not relent' (Numbers 23:19). This is resolved by understanding that divine relenting is God's responsive faithfulness — when circumstances change (repentance, prayer), God's actions change accordingly, consistent with His consistent character. Isaiah 40 opens with 'Comfort, comfort my people' — God sending His word to bring nacham to exiles.