doppelt

In a sentence

• Ich habe doppelt so viel Obst gekauft wie letztes Mal.

  I bought twice as much fruit as last time.

  Here, 'doppelt' is used to indicate a quantity that is twice as large as another specified amount.

• Diese Tür ist doppelt gesichert, damit sie besonders sicher ist.

  This door is doubly secured to ensure it is especially safe.

  In this sentence, 'doppelt' describes the intensification or redundancy of an action (securing).

• Ich sehe alles doppelt, wahrscheinlich wegen meiner neuen Brille.

  I am seeing everything double, probably because of my new glasses.

  Here, 'doppelt' conveys a repeated impression, in this case, a visual doubling.