Roger Woodham replies:'Incredible' and 'unbelievable'
These
two adjectives, incredible and unbelievable, are quite
interchangeable and to these two you could add a third: unimaginable.
They
all describe things or events which are so amazing that they cannot
be imagined or believed.
Adverbial
forms are incredibly, unbelievably and unimaginably.
You can substitute any of these adjectives or adverbs under discussion
as you wish:- 'When she died, Aunt Isobel left me an incredible amount
of money ? so much I didn’t know what to do with it!'
- 'I intend to work
incredibly hard over the summer so that I pass my exams in September.'
- 'My performance at the Christmas concert was unbelievably bad.'
- 'The weather
on the mountain yesterday was unbelievable. There was no chance of
us getting to the top.'
- 'The operation was performed under almost unimaginable
conditions. It is unbelievable that he survived.'
- 'The new computer
game was unimaginably difficult. Neither Mike nor I could work out
how to progress from level 1 to level 2.'