contradict : 指肯定地否认、反对或反驳某事，坚持相反的意见。
- If you're both going to lie, at least stick to the same story and don't contradict each other!
- He kept contradicting himself when we were arguing - I think he was a bit confused.
- How dare you contradict (me)!
- Recent evidence has contradicted established theories on this subject.
deny : 普通用词，侧重否认意见或言论的真实性，尤指否定他人的指控或责难。
- He will not confirm or deny the allegations.
- Neil denies that he broke the window, but I'm sure he did.
- Neil denies breaking the window.
oppose : 普通的广泛用词。指不作争论或不提出论据而无理由地反对；也指任何温和、有理由的反对或否定。
- The proposed new testing system has been vigorously opposed by teachers.
- Most of the local residents opposed the closing of the school.
- I would certainly oppose changing the system.
refute : 语气较强，强调凭推理或证据驳斥一项主张或言论。
- to refute a person/theory/argument/claim
- She refutes any suggestion that she behaved unprofessionally.
- It was the kind of rumour that it is impossible to refute.
- Isabelle is quick to refute any suggestion of intellectual snobbery.