Check: You make a Knowledge check to see if your character knows something.
The DC for answering a question within your field of study is 10 for easy questions, 15 for basic questions, and 20 to 30 for tough questions.
Try Again?: No. The check represents what you know, and thinking about a topic a second time doesn't let you know some-thing you never knew in the first place.
Special: An untrained Knowledge check is simply an Intelligence check, Without actual training, a character only knows common knowledge about a given subject.
You can take 10 when making a Knowledge check, but you can't take 20.
A character with the Educated feat gets a +2 bonus on any two types of Knowledge checks.
The GM may decide that having 5 or more ranks in a specific Knowledge skill provides you with a +2 synergy bonus when making a related skill check, For example, a character with 5 or more ranks of Knowledge (Life sciences) could get a +2 synergy bonus when making a Treat Injury check in certain situations.
Time: A Knowledge check can be a reaction, but otherwise requires a full-round action.