- A-Line Announcements (A-Style Envelopes) – Two side-seam envelopes with a deep wallet flap and a deep throat normally manufactured from text grade papers and used for announcements, invitations, and social stationary.
- Air Mail Envelopes – Lightweight envelopes designed to keep the weight (and postage) to a minimum. Feature a red and blue border with "Air-Mail" printed on them.
- Back – The backside of the envelope where the pocket is formed.
- Back Seam – The seams formed by the overlap of the bottom flap and the side flap.
- Bangtail – Booklet style envelope featuring a perforated extension on the back throat area of an envelope. They are most commonly used on remittance envelopes to advertise products or services.
- Banker Flap Envelope – Also referred to as a Wallet Flap, this envelope has a seal flap that is straight across and often used for mailing heavier materials like bank statements.
- Baronial – Style of envelope that typically has diagonal seams with a pointed flap. It is often used for invitations, greeting cards, and social stationary.
- Blocking – Seal flap is stuck to envelope back at the seams.
- Bond Grade – Grade of paper typically used for letterhead with matching envelopes. This grade often includes cotton fibers and is desired for its strength, low opacity, and other positive characteristics.
- Booklet Envelope – Open-side double side seam envelopes usually used for advertising mail because they can be machine inserted.
- Bottom Flap – Portion of the envelope which forms the bottom boundary of the pocket.
- Brightness – Used to measure the light reflecting properties of the envelope paper. Brighter papers typically provide the best quality prints.
- Business Mailer – Open side envelopes with center seams. Often used where extra strength is needed.
- Business Reply Envelopes – (BRE) Envelopes sized to accompany direct mail or invoices that are printed with postal service approved copy that indicates the return postage will be paid by the original mailer.
- Catalog Envelopes – Open-end envelopes typically used for mailing sales catalogs and large unfolded material. Typically need to be hand inserted.
- Cellophane – Extremely clear cellulose patch material for window envelopes.
- Center Seam – Back seam which forms in the center of the width of the envelope.
- Clasp – Metal pronged closure.
- Closures – General term for the various methods used to secure the seal flap to the back of an envelope. Can include seal gum, clasp, and string & button.
- Coin Envelopes – Small open-end envelopes as small as 1-11/16" x 2-3/4" that are often used for holding small parts and coins.
- Commercial Flap – Contoured seal flap.
- Commercial Style – Most commonly used business envelope. Features an open-side style with either a diagonal or two side seam.
- Coupon Hitch Hiker – Remittance envelope with a perforated sheet that extends from the flap.
- Diagonal Seam – Seams running diagonally from the bottom of the envelope to the throat forming the pocket.
- Die-Cut – Industry term that describes the process of cutting envelope blanks utilizing a high die.
- Document-Legal – Open-side envelopes with outside seams often used for legal documents such as deeds and titles.
- Double Side Seam – Back seams running vertical on both sides.
- Drug & Pay Envelopes – Small open-side envelopes often used to dispense pills.
- Expansion Envelopes – Also referred to as gusseted envelopes, these envelopes feature accordion like sides that expand to accommodate larger items. Typically used as shipping envelopes.
- Face – The front of the envelope.
- FIM (Facing Identification Markings) – A group of vertical lines placed on the top of business reply and courtesy reply mail which enables automated mail processing equipment to identify it and separate it from other mail.
- Finish – The surface characteristics of paper stock, such as luster, or texture which differs from grade to grade. Different finishes have varying degrees of printability, smoothness, and ink receptivity.
- First Class Mailer – Envelopes featuring a border with diamonds and the words "First Class" typically printed on them in the color green.
- Flaps Extended – Seal flap that is scored but not folded down.
- Flexographic Printing – Inexpensive printing process often used for high volume applications with relatively easy to print artwork.
- Fold – Any folded edge of an envelope such as the side fold, top fold, or bottom fold.
- Flush Cut – Top of envelope cut straight across.
- Glassine – Chemically treated paper patch material that has a cloudy opacity. It is biodegradable and recyclable, but has lost a lot of its popularity to more transparent and durable polystyrene materials.
- Gum – The adhesive used on most paper envelopes. Typical varieties are moisture activated, but latex gums are also common.
- Hitch Hiker Envelope – Envelopes featuring extended flaps that get filled out, torn and inserted back into a remittance envelope.
- Inside Tint – A printed design placed on the inside of an envelope to provide added security so that the contents of the envelope cannot be seen through the paper.
- Indicia – Pre-printed postage permit in the upper right hand corner of an envelope showing the envelope does not need a stamp.
- Jet Imprinting – Printing method often used to print on assembled envelopes with high quality and a quick turnaround time.
- Laidline – A type of paper with a lined appearance.
- Latex – Self-sealing gum on a seal flap.
- Litho (Lithographic) Printing – Form of printing commonly used in the envelope processing industry. See Offset Printing.
- Offset Printing – Also referred to as lithographic printing, this process offers the best quality and clarity of any printing process and can be used for multiple colors or 4-color process prints.
- Opacity – A term used to describe a material's ability to limit light from passing through it. The more opacity the paper has, the less one can see though it. Inside tints, however, are often used to make inexpensive papers with low opacity more opaque.
- Open End Envelopes – Envelopes with the opening and seal flap on the shorter dimension.
- Open Side Envelopes – Envelopes with the opening and seal flap on the longer dimension.
- Panel Cut – Uncovered window.
- Patch – Name given to the material used to cover the window cut out. Typically polystyrene, cellophane, or glassine.
- Peel & Seal – Pressure sensitive seal gum with release paper cover.
- Pocket – The pouch formed by sealing the side flaps and the bottom flaps.
- Policy Envelopes – Open end envelopes for documents.
- Poly – Popular plastic window patch film.
- Preview Window – Full face window for booklet envelopes.
- Regular – Industry term used to describe any commercial envelope that does not have a window.
- Remittance – Two side seam envelope with deep wallet flap used for return mail of checks.
- Seal Flap – Portion of the envelope which carries the closure (either adhesive or mechanical).
- Seal Gum – The adhesive used to seal the seal flap to the back of the envelope securing and completing the enclosure. Normally, it is remoistening gum which is activated by moisture. However, self-sealing latex and pressure sensitive gum are also used for specific purposes.
- Shoulder – The top edge of the side flaps at the envelope opening.
- Side Flaps – These are the parts of the envelope which form the side boundaries of the pocket enclosure. Most are folded over and mate with the bottom flap at the diagonal seam to create the pocket. They may, however, be vertical for single or double side seams.
- Side Seam Over – Side seam folds over back flap. Same as outside side seam.
- Side Seam Under – Side seam folded under the back flap – same as inside side seam.
- Single Side Seam – One back seam running vertical on one side.
- Split Seal Gum – Gum pattern featuring blank spaces that prevent the flap from adhering to the back panel during storage.
- Throat – The measured space from the top fold line to the top of the pocket. This measurement is taken at the center of the width of the envelope.
- Thumb Cut – Thumb shaped cut on envelopes with no seal flap.
- Tinting – See Inside Tints
- Tyvek® – A synthetic, ultra-lightweight paper made by the DuPont Corp used extensively for shipping envelopes due to its durability, tear resistance, a waterproof properties.
- Wallet Flap – Seal flap that is straight across. See also...Bankers Flap Envelopes
- Web Cut – Envelopes manufactured from a continuous roll of paper that is fed into a converting machine and cut with inline rotary knives rather than dies.
- Window – Cut out opening on face or back of envelope that is usually patched.
- Wove – The most common form of envelope paper, it features a uniform surface and a soft, smooth finish with relatively low opacity and a very economical price.