Hi Nanako Conclusive : means that a conclusion has been reached - all the evidence shows that there is a final conclusion or result. For example: "the laboratory tests were conclusive: analysis showed that the man had been poisoned. Ther was no mistake".. Decisive: is the action of a person who makes a decision about something/decides to do something. For example: "following several accidents on this part of the road, the Police and local Council took decisive action and closed the road for repair work". So, they made the decision to close the road as it was dangerous Therefore, " it proves conclusively that he stole the bike" is correct. You would not use decisive here. And "there is conclusive evidence about this case" is also correct. You would not use decisive here either. I hope this helps?

Great question! They are quite similar and are often used interchangeably. However, they do not have exactly the same meaning, so in some cases you would use one instead of the other. Conclusive relates to a conclusion, so is basically about finding the answer to something. Decisive is more about making a decision, so if it is decisively proven the answer has been decided, rather than concluded. Talking about evidence in court you would usually say it is conclusive, so it shows the answer for whether someone is guilty or not. Sometimes it doesn't matter, but in science or law you want the facts to conclude something rather than be decided. Some examples: The victory was decisive. She thinks quickly and is decisive. The study conclusively showed the medicine worked as a cure. The evidence conclusively showed he was innocent. The jury decisively replied, "Not guilty".

Hi, Nanako. Let's see, decisive-adj: *an action, event etc that is decisive has a big effect on the way that something develops *definite and clear in a way that leaves no doubt (actions/steps/answers) Ex: Women can play a decisive role in the debate over cloning. We will take decisive steps towards political union with Europe. He has a talent for quick decisive action Her aswer was decisive. conclusive-adj: *showing that something is definitely true (conclusive proof/evidence/findings etc) Ex:The investigation failed to provide any conclusive evidence. We still have no conclusive proof that Walters was at the scene of the crime. They have been able to collect some data, but as yet nothing really conclusive. So, as you see, "decisive" is used to say that something is clear or important; "conclusive", on the other hand, is used to say that something is real or is proving something else. Hope it'll help.