Issue

Issue is widely used to mean a single release of a periodical: a daily, weekly, monthly, or quarterly instalment of a newspaper or magazine is an issue; the collected issues of (usually) a year together form a volume.

In bibliography, however, issue has a more precise meaning: it is a ???.

Issue shouldn’t be confused with edition, printing/a>, or state.

Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.