Keycap terminology becomes much easier once you separate five ideas: how a cap mounts, where it sits, how large it is, what shape it has and how it was made. Use this glossary as a plain-English reference, then follow the linked guides when a term affects compatibility, feel, lighting or buying decisions.
The hobby has collected a large vocabulary for small pieces of plastic. Some of it is precise; some is informal; and some product listings use the same word for several different things. That is why this glossary explains what a term tells you—and what it does not prove.
If you are starting from zero, read the Complete Guide to Keycaps first. If one mysterious abbreviation is standing between you and checkout, use the contents below and go directly to it.
Article method and source note
Author: Thekapco Editorial Team
Technical reviewer: Timo, Senior Executive at Thekapco
Publication date: 21 September 2026
Last reviewed: 21 September 2026
This glossary consolidates terminology from Thekapco's completed fit, material, profile, care and collecting guides. Mechanical-switch construction was checked against CHERRY's published MX explanation; keyboard matrix and layer language was checked against QMK documentation; compatibility language was checked against manufacturer guidance and Thekapco's current product standard. Terms can vary between manufacturers, so the exact product specification remains final.
In this guide
- How to use the glossary
- Units and key sizes
- Layout and kitting terms
- Stem and switch terms
- Profile and shape terms
- Material terms
- Legend and manufacturing terms
- Lighting terms
- Artisan and collecting terms
- Care and quality terms
- Frequently asked questions
How to use this glossary
Begin with the category matching your question. A fit problem usually lives under units, layouts, stems or kit coverage. A comfort question usually begins with profile and shape. A durability or appearance question may involve material, legend method, coating and daily use together.
Category names are not quality grades
PBT is not automatically better than ABS. Doubleshot is not automatically better than dye-sublimation. A taller profile is not automatically more premium, and a 140-key kit is not automatically more compatible than a smaller kit.
Each term describes one property. Quality comes from how the entire product is designed, manufactured, inspected and matched to its intended keyboard.
Compatibility needs several terms at once
A set can be MX-style, ANSI and full-size compatible yet still miss an unusual bottom-row key. Treat every compatibility phrase as one check in a sequence, not as a magic password.
Units and key sizes
1u
The reference width of a standard letter or number key. Other key widths are described as multiples of this unit. The number refers to nominal keyboard spacing, not a measurement you should reproduce with a kitchen ruler to the nearest millimetre.
1.25u, 1.5u and 1.75u
Common modifier-key widths. A familiar ANSI bottom row often uses 1.25u modifiers, while compact boards may use 1u or 1.5u keys and many 65% or 75% boards use a 1.75u right Shift. The location and row shape still matter.
2u, 2.25u and 2.75u
Widths often seen on Backspace, Enter and Shift keys, depending on the layout. Wide keys generally use stabilisers as well as the central switch.
6.25u and 7u Spacebar
Two common Spacebar widths. A 6.25u Spacebar is common on standard ANSI arrangements; 7u appears on some enthusiast and alternative bottom rows. Width alone does not confirm that the stabiliser mounting positions match.
Thekapco's current full-set standard uses a 6.25u Spacebar, 1.25u default bottom-row modifiers and 1u extra keys. Always check the current included-key diagram because a future kit can change.
Stabilised key
A wide key supported by a stabiliser so both ends travel more evenly. Spacebar, Enter, Shift and Backspace commonly fall into this group. A keycap can match the centre switch stem but fail at the stabiliser mounts.
Layout and kitting terms
Physical layout
The real arrangement, size and position of keys and switches. ANSI, ISO and JIS describe physical layout families. The operating-system language does not move the Enter key or change the Spacebar.
Logical layout
The characters or commands the computer assigns to physical positions, such as QWERTY, QWERTZ, AZERTY, Dvorak or a custom mapping. Logical layout affects legends and typing behaviour, but it is separate from the cap's physical size.
ANSI
A common physical layout family recognisable on many boards by a wide rectangular Enter and a longer left Shift. Thekapco's current standard focus is ANSI.
ISO
A physical layout family commonly using a taller Enter and an extra key beside a shorter left Shift. No current Thekapco keycap set supports ISO as of 14 September 2026. Future support must be confirmed on the exact product.
JIS
A Japanese physical layout family with additional language keys and a different Spacebar area. Japanese sublegends printed on an ANSI set do not turn it into a JIS kit.
Keyboard percentage
A broad size label such as 100%, TKL, 75%, 65% or 60%. It tells you which groups of keys are generally present, but manufacturers can implement the same percentage with different right Shift, bottom-row or navigation-key sizes.
Kit
The exact group of keycaps sold together. A base kit, numpad kit, spacebar kit or novelty kit may cover different sections. The kit contents—not the product-family name—decide what arrives.
Kit coverage
The layouts and key sizes the exact kit can physically populate. Coverage should be proven by an included-key diagram, not inferred from a large total key count.
Included-key diagram
A top-down inventory of every keycap in the set. This is one of the most useful compatibility documents on a product page. Read it key by key rather than admiring it as decorative geometry.
Row label: R1, R2, R3 and R4
A label for a keycap's intended profile row. The numbering direction is not universal across every manufacturer, so check that maker's diagram. On a sculpted set, a key of the correct width can still feel or look wrong when installed on the wrong row.
Stem and switch terms
Keycap stem or socket
The structure under the keycap that connects to the switch. People may say “stem” for the switch's moving centre and also for the keycap socket, so use context carefully.
Switch stem
The moving part at the top of a switch. It supports the keycap and moves during a press. Its colour may suggest a switch model or feel, but colour alone does not prove the mounting interface.
MX-style cross stem
A cross-shaped mounting family based on the familiar CHERRY MX interface and used by many switches and keycaps. “MX-style” is broad: it does not guarantee identical tolerances, nor does it prove layout coverage.
Low-profile switch
A shorter switch system designed for a lower overall keyboard. Low-profile families may use different stems, stabilisers and cap geometry. Do not treat them as standard-height MX switches that have simply had a haircut.
Hot-swap
A keyboard feature allowing supported switches to be removed from sockets without soldering. Hot-swap describes switch installation, not automatic compatibility with every switch or keycap.
Linear, tactile and clicky
Broad switch-feel categories. Linear switches move without a tactile bump from the switch mechanism; tactile switches provide a noticeable bump; clicky switches add an intentional click mechanism. Keycaps can influence overall sound, but they do not convert one switch category into another.
Actuation
The point at which a switch registers a press. It can occur before the key reaches the bottom of its travel. Actuation belongs mainly to the switch and keyboard system, not the keycap.
Profile and shape terms
Keycap profile
The keycap family's height, top shape and row geometry. Cherry, OEM, ASA, XDA and MOA are profile names. The same material can be made in different profiles.
Sculpted profile
A profile in which different rows use different heights, angles or shapes to create a contour across the keyboard. Row placement matters on sculpted sets.
Uniform profile
A profile using substantially the same shape across rows. Uniform profiles can make rearranging legends easier, but individual keys can still have different widths or special shapes.
Cylindrical, spherical and flat top
Terms describing the top surface or dish. Cylindrical tops curve mainly across one direction; spherical-style dishes curve in more than one direction; flatter tops have less pronounced shaping. Naming can vary between makers.
Cherry profile and OEM profile
Two familiar sculpted families. Cherry is generally lower than OEM, but exact dimensions and tooling vary by manufacturer. “Cherry profile” describes a shape family; it does not mean the product was made by CHERRY.
ASA, XDA and MOA
Other profile families encountered in current products. ASA is a sculpted family; XDA is relatively low and uniform; MOA is known for a rounded, uniform appearance. Preference should be tested on the exact product and keyboard rather than decided by a profile-name popularity contest.
For the full comparison, use the Complete Keycap Profile Guide.
Material terms
ABS
Acrylonitrile butadiene styrene, a thermoplastic widely used for keycaps. ABS can support strong colour and moulding options. Surface shine can develop with use, but texture, thickness, tooling and finish vary by product.
PBT
Polybutylene terephthalate, another common keycap thermoplastic. PBT is often selected for texture and resistance to visible shine, but it is not immune to wear and does not guarantee a good product by itself.
PC or polycarbonate
A thermoplastic that can be transparent or translucent and is useful when the body, sides or artwork are intended to interact with light. Clear surfaces may show scratches or handling marks differently from opaque caps.
PC/PBT
A product description indicating that polycarbonate and PBT are both used somewhere in the construction. It does not define one universal recipe. Check which part uses each material.
Resin artisan
A keycap or decorative cap made partly or wholly from resin, often through casting and hand-finishing processes. Fit, weight, height, clearance and maker care all need checking.
Thickness
The wall or structural thickness of a keycap. It can influence rigidity and sound on a specific keyboard, but thickness does not act alone; profile, material, cavity, switch, plate, case, stabilisers and desk all contribute.
Legend and manufacturing terms
Legend
The letter, symbol or artwork on a keycap. A legend can be moulded, printed, sublimated, engraved or coated depending on the construction.
Sublegend
A secondary symbol or character set, often placed beside or below the main legend. Sublegends can describe alternative inputs, language characters or a visual theme; they do not change physical layout.
Dye-sublimation or dye-sub
A process using heat to transfer dye into a compatible keycap surface. It is different from a surface sticker or ordinary wet ink. Colour and substrate relationships place practical limits on what can be achieved.
Reverse dye-sublimation
A dye-sub approach in which a broader background area is coloured while selected legend or design areas remain lighter. It creates different design possibilities and production challenges from a simple dark-on-light legend.
Doubleshot
A moulded construction using separate shots of plastic so the legend is formed as a different piece of material rather than printed on the surface. It does not automatically mean shine-through, perfect alignment or superior overall quality.
UV printing
A printing process in which deposited ink is cured with ultraviolet light. It can support detailed, colourful artwork on suitable surfaces. Performance depends on ink, preparation, coating, geometry, curing and use.
Pad printing and laser marking
Other ways to apply or create legends. Pad printing transfers ink from a pad; laser methods can mark or remove surface material or coating. The process name alone does not tell you how the finished legend will age.
Novelty key
A keycap carrying decorative artwork or a non-standard legend, usually supplied as an optional replacement for a regular key. “Novelty” describes its visual role, not its size or compatibility.
For the manufacturing comparison, see Dye-Sub vs Doubleshot Keycaps.
Lighting terms
Shine-through legend
A legend designed to transmit backlight through the character. A keycap may be doubleshot without being shine-through, and a translucent body does not guarantee a brightly illuminated legend.
Translucent or transparent body
A body that allows some or substantial light through the material. Results depend on pigment, wall thickness, surface treatment, LED position and keyboard design.
Pudding keycap
A keycap with translucent sidewalls or a broad translucent section intended to show more keyboard lighting. “Pudding” describes the visual construction, not one fixed material, profile or fit standard.
North-facing and south-facing LED
Informal descriptions of LED/switch orientation on many boards. Orientation can affect how legends are illuminated and, on some combinations, cap/switch clearance. Check the exact keyboard, switch and profile rather than assuming the compass point settles everything.
Artisan and collecting terms
Artisan keycap
A keycap made as an individual art object or small-series work, often sculpted, cast, painted or assembled by a maker. The term does not guarantee handmade construction, authenticity, fit or official licensing unless those points are separately stated.
Accent key
A single keycap or small group used to contrast with the main set. Escape and Enter are common positions, but size, row and clearance still apply.
Colourway
The planned colour arrangement used across a keycap set or product family. Two sets can share a profile and material while having entirely different colourways.
Group buy
A time-limited ordering model in which production may begin after orders are collected. Timelines, cancellation terms, minimum quantities and fulfilment risk vary by organiser; read the specific terms.
In-stock release
A product sold from inventory already held or allocated by the seller. “In stock” describes availability at that moment, not permanent availability or universal shipping access.
Officially licensed
A product made under authorisation connected to the relevant intellectual-property owner or authorised licensing chain. Licensing, product quality and compatibility are three separate questions.
Care and quality terms
Surface shine
A smoother or glossier area that can develop where fingers repeatedly contact a cap. It can be normal wear rather than dirt. Aggressive scrubbing cannot restore original texture and may make the surface less even.
Warping
A shape deviation in which a cap—often a wide Spacebar—does not sit as intended. Whether it is acceptable or defective depends on the product specification, reference, severity and effect on installation and use.
Alignment
The position and orientation of a legend or artwork relative to the approved reference. Evaluation should account for exact key size, viewing method, print method and documented acceptance criteria.
Approved sample or reference
The physical or documented version used to compare production. At Thekapco, physical sampling, colour and alignment review, supplier inspection reporting and final approval are separate parts of production control.
Acceptable variation
A difference that remains within the approved specification and does not prevent normal fit, use or presentation. Handmade and mass-produced items can have different expected variations; neither category excuses a functional defect.
Defect
A condition outside the approved specification or seller's stated standard, such as missing kit contents, structural cracking, unusable fit or unacceptable production deviation. Customer Service and Procurement assess evidence and decide replacement or refund outcomes under the applicable policy.
Frequently asked questions
What does “u” mean in keycaps?
It is the unit used to describe key widths relative to a standard 1u letter key. It helps compare Spacebars, modifiers and Shift keys, but stabiliser positions and profile rows still need checking.
Are all MX-style keycaps interchangeable?
No. The cross mount is only one compatibility layer. The keyboard's physical layout, key sizes, stabilisers, profile rows and exact kit contents must also match.
Is PBT always better than ABS?
No. They offer different manufacturing, colour, texture and ageing possibilities. Product quality depends on the entire design and process. Read ABS vs PBT Keycaps for the detailed comparison.
Does doubleshot mean the legends light up?
No. Doubleshot describes a multi-part moulded construction. Shine-through requires the legend material and complete keyboard lighting path to transmit light.
Why does the same term mean different things on different sites?
The keyboard industry does not use every profile, row and construction label identically. When a term affects fit, treat the manufacturer's current diagram and product specification as the final definition for that item.
What should I learn before buying my first set?
Learn enough to check stem, physical layout, key sizes, Spacebar, profile and included-key coverage. You do not need to memorise this glossary. You need to recognise which specification answers which question—which is more useful at checkout and kinder to your memory.