sonuna

In a sentence

• Yürüyüşün sonuna geldik.

  We have reached the end of the walk.

  Here, 'sonuna' means 'to the end', referring to the conclusion of the walking activity.

• Kampanya ayın sonuna kadar devam edecek.

  The campaign will continue until the end of the month.

  In this case, 'sonuna' indicates a specific point in time, namely the conclusion of the current month, as a temporal reference.

• Kitabın sonuna bir ek eklemeyi düşünüyorum.

  I am considering adding an appendix at the end of the book.

  Here, 'sonuna' refers to the conclusion or the last part of the book, as a spatial reference.