Grammar fix
seriously doubt
not believe
To strongly think that something is not true or will not happen.
collocationB2common
Hear it in context
Notice where the phrase sounds natural.
I seriously doubt he will finish the project on time.
To be honest, I seriously doubt that most people recycle as much as they should, even though they know it's important.
Fix the pattern
One small grammar move makes it sound right.
Not: I seriously doubt that he will not come.
Say: I seriously doubt he'll come. (= I don't think he will)
'Doubt' already means 'don't believe' — don't add a second negative.
Which sounds natural?
Tap the one a native speaker would say.
Natural; 'harbour grave reservations' is formal/legalistic.
Build natural chunks
Words that usually travel with it.
seriously doubt
- whether
- that
- I
- very much