It's highly unlikely that they will make a breakthrough in the near future. (doubtful)
It is doubtful that they will make a breakthrough in the near future.
It is vaguely possible that we'll be able to travel to Mars by 2050. (inconceivable)
It is not inconceivable that we'll be able to travel to Mars by 2050.
I'm sure they'll notice it's missing. (bound)
They're bound to notice something is missing.
We can't be entirely confident that the family haven't already been informed. (chance)
There is a slight/remote chance that the family haven't already been informed.
We're being met at the airport so we don't need train tickets. (presumably)
We're being met at the airport so presumably we don't need train tickets.
Unfortunately, he doesn't stand a chance of getting the job.
Unfortunately, he doesn't have have a hope of getting the job.
China has a good chance of winning the space race. (distinct)
There is a distinct chance/possibility that China will win the space race.
There doesn't seem to be much hope that the relationship will improve. (doubt)
I doubt whether the relationship will improve.
