Scientific literature has items called letters, communications and journal papers. They all seem quite similar in terms of format and content. What are the differences between them?
In physics, each category has a different length limit. Often "paper" has no limit. Typically the shorter the length limit, the more prestigious it is and the tougher the acceptance criteria. The subject matter covered by the journal is the same for all categories. Some journals also have a "review" category which includes papers which are not original research. Often a review is by invitation only.
This will depend wildly on the field and journal in question. In my experience, the main differentiators are the allowable length and the amount of peer review. For example, in my field (Epidemiology):
- Journal Article (of which there are several categories): Word limit in the several thousands of words, full on peer review.
- Communication (often also called 'Brief Report'): A smaller <2000 word word limit with further restrictions on the number of tables and figures. Goes out for full peer review. This is intended to report a single, small finding that may not warrant a full publication.
- Letters: This is a very ambiguous category, primarily defined by being short, often <1000 words. They may be used to report a single piece of information, often from part of a larger study, or may be used to respond to another paper. These may or may not go out for peer review - for example, I recently had a paper accepted where the decision was made entirely by the editor.