If the classroom door is open, that is a signal that you're not too late. BUT, if the classroom door is closed, you are TOO LATE for that class meeting. Each student is entitled to miss the equivalent of one week of class without penalty. However, a student should use the 2 or 3 discretionary absences in the same way a football or a basketball coach uses timeouts. Words as well as ideas are intellectual property and can be stolen as easily from another person as money or an automobile.
Armed robbery is a form of theft and so is plagiarism.
Plagiarism is easy to do. Always give credit when you use the work of others. Most students who have gone through the grades can remember long hours of copying articles out of encyclopedias. In college, this is plagiarism. You must not use other people's work or words and present them as your own.