Always allow editing and Duplicate entries allowed are two separate settings. However, they can work together in an interesting way.
If you turn on Always allow editing, students can edit entries that have already been made. So, if two students have different definitions for a term, they can each contribute their definition to the same entry. In this case, the second student will not need to create a duplicate entry; they can just add their definition to the existing entry.
If you turn off Always allow editing, consider allowing duplicate entries. Then, if two students have different definitions for the same term, they can each create an entry for that term.
