Certain words are so closely related that people have become accustomed to using them interchangeably even where they don't apply. Lecterns and pulpits are examples of these.
The confusion arises because while pulpits are technically lecterns, not all lecterns are pulpits. A lectern is simply any platform that is raised enough to accommodate objects placed on it such as books or notes.
Pulpits, on the other hand, are similarly raised platforms but are meant to be used strictly in religious environments. So while all pulpits are technically lecterns, not all lecterns are pulpits.
A lectern becomes a pulpit only when it is used in a religious sense, such as in a church service. Additionally, pulpits can become ordinary lecterns if they stop being used in a religious environment.
So in short, the difference between both terms is only in their usage.
