Songfacts®:

• A delta is where the river meets the ocean. In this song it represents the transition from the calm, closeted world of touring to the wild oceans of the real world when the band members came face to face with the trials of life outside of music. These included keyboardist Ben Lovett's divorce and Marcus Mumford witnessing the death of his grandmother.
• "Delta" used to be two separate songs before they were combined. The band explained: "It was in the sort of patchwork quilt process in the record-making process where you can cut things up and patch them back together again, and it used to be a very, very, very long song and now it's just a quiet long song."
• Lovett explained to the BBC there were many reasons why the band named their fourth album after this song.
  
  "First, there's the concept of the River Delta and how the rivers and oceans interact. The river is the gateway between the tranquillity and safety of the river and the wild unknown of the ocean. So that ties thematically into a lot of the lyrics - that transitional thing of facing up to life."
  
  "Delta is also the fourth letter in the phonetic and Greek alphabet; and this is our fourth album. A lot of bands' fourth records are the ones that define them - and I feel like this could be the one that defines us."