primary transcript (pre-mRNA)
/ PRY-mair-ee TRAN-skript, pree-EM-ar-en-AY /
When RNA polymerase finishes transcribing a gene in one of your cells, the strand it produces is not yet a usable message. It is more like a rough first draft — complete, but full of material that has to be edited out, and missing the protective bits a finished message needs. This raw, freshly made RNA, before any editing, is the primary transcript. For protein-coding genes it is also called pre-mRNA, because it is the precursor that will become mature messenger RNA.
Concretely, the primary transcript is the direct, unprocessed product of transcription. In eukaryotes it contains both the useful parts that code for the protein (exons) and stretches of filler that do not (introns), all strung together in one long molecule. Before it can leave the nucleus and be translated, it must be processed: a protective cap is added to its front, a tail of repeated A's is added to its back, and the introns are cut out while the exons are stitched together by splicing. Only after all this editing is it a mature mRNA.
This draft-then-edit arrangement is a hallmark of eukaryotic cells and a major difference from bacteria, where a transcript is often used as-is. The extra processing steps are not wasteful red tape — they protect the message, control how long it survives, and (through alternative splicing) let one gene yield several different proteins. The primary transcript is the canvas on which all that editing happens.
A draft essay you have just typed is like a primary transcript: the ideas are all there, but you still need to add a title page (cap), staple the pages (tail), and delete every digression (introns) before handing in the clean final copy (mature mRNA).
The primary transcript is the rough draft; capping, tailing, and splicing turn it into a finished mRNA.
Only eukaryotes routinely make and process a pre-mRNA inside a nucleus; bacteria, having no nucleus, often start translating a transcript before it is even finished.