Swords · Anatomy
Anatomy of a Katana刀の各部
Every part named and explained, from the tip to the tang
A Japanese sword looks simple from across a room: a single curved line of steel. Up close it is a vocabulary. Nearly every ridge, notch, and surface has a name, because for centuries these features were how smiths, polishers, and appraisers described a blade, judged its quality, and traced its maker. Learning that vocabulary is the fastest way to actually see a sword rather than just look at one.
This page walks the blade from tip to tang, then moves to the mounting, the fittings that turn a bare blade into something that can be carried and used. Along the way we point out where the same ideas reappear in a kitchen knife, because they are the same craft seen from two angles. Okami is a kitchen-knife house; we cover swords as history and craft and we do not sell them. Kanji are given in their standard Japanese forms, with romaji, so you can recognize the terms wherever you meet them.
A quick orientation before the details. A sword has a hardened cutting edge along one side, a thicker unsharpened back opposite it, a curve that runs the length of the blade, a distinct tip section set off by its own small line, and a tang hidden inside the handle that carries the maker's signature. Hold those five ideas in mind and the rest slots into place.
The Blade, Labeled
A line diagram of a katana blade with its principal parts marked
Blade Geometry: Edge, Spine, and the Ridge Between
The three long lines that run the length of the blade
Look at a katana in cross section and it is not a simple triangle. The classic profile, called shinogi-zukuri, has three surfaces per side that meet along distinct lines. Reading those lines is how a polisher decides where to remove metal and how a viewer judges the geometry.
Ha
The sharpened edge itself, running the underside of the blade. It is the hardest steel on the sword and the part that does the cutting. The kitchen knife inherits this directly: on a gyuto the ha is the working edge you sharpen on a stone.
Mune
The unsharpened back of the blade, opposite the edge. On a katana it is often ridged (iori-mune, a peaked back) rather than flat. The mune carries the sword's curve and much of its strength, the way a knife spine gives a blade its rigidity.
Shinogi
The raised ridge running lengthwise between the flat upper surface and the ground edge bevel. It defines the shinogi-zukuri shape. A clean, straight shinogi is a mark of good geometry and good polishing. Some Japanese single-bevel kitchen knives carry their own shinogi line for the same reason.
Shinogi-ji and Hira
The shinogi-ji is the narrow flat between the shinogi ridge and the spine; the hira is the broader flat surface of the blade below the ridge. These are the surfaces where the grain of the steel (hada) and the polish are most visible.
Iori-mune and other spine shapes
Seen end-on, the mune is not flat but usually peaked, a form called iori-mune (a gabled or "roof" back). Other shapes exist, including a flat back (kaku-mune) and a rounded one (maru-mune). The spine profile is a small but real part of how a blade is described and attributed.
Inside the blade: lamination
Many Japanese swords are not one steel but several forge-welded together, so a hard, high-carbon edge is backed by a tougher, lower-carbon core or skin. Standard names describe the arrangement: maru (a single steel throughout), kobuse (a hard jacket wrapped around a softer core), and honsanmai, often just sanmai (a hard edge and skin supported by tougher outer layers). This hard-over-tough construction is exactly the logic behind laminated and clad Japanese kitchen knives, where a hard cutting core is clad in softer stainless or iron.
The Tip and Its Boundary
The kissaki, the yokote that frames it, and the boshi within
The tip of a katana is treated almost as a small sword of its own. It is set off from the body by a short, crisp line and has its own section of temper. Appraisers pay close attention here, because the tip is one of the hardest parts to forge and polish well, and it is the first area to suffer if a blade is damaged or clumsily reshaped.
Kissaki
The pointed tip section of the blade. Its size is described in relative terms, from ko-kissaki (small) through chu-kissaki (medium) to o-kissaki (large), and the proportion is one clue to a blade's era and school.
Yokote
The short straight line that separates the kissaki from the body of the blade. On a properly finished shinogi-zukuri blade the yokote is crisp and well defined; a blurred or missing yokote usually signals wear or an amateur polish.
Boshi
The portion of the temper line that runs through the kissaki. Its shape, and the way it turns back toward the spine (the return, or kaeri), is a named feature in its own right, with forms such as ko-maru (small round). A healthy boshi is essential; if it runs off the tip, the blade is considered seriously compromised.
Where Blade Becomes Tang
The notches, the hidden tang, and the peg that holds everything together
The transition from the polished blade to the rough tang is marked by two small notches, and everything below them lives inside the handle, unseen in normal use. To a collector, though, the tang is the single most informative part of the sword.
Ha-machi and Mune-machi
The two small notches that mark where the sharpened blade ends and the tang begins: the ha-machi on the edge side and the mune-machi on the spine side. They locate the habaki collar and are a fixed reference point for measuring the blade.
Nakago
The unpolished extension of the blade that sits inside the handle. It is left with its forged surface and file marks, and it carries the smith's signature (mei) when one exists. Because the tang is rarely reworked, its shape, patina, and file pattern are prime evidence of age and authorship. (The Edo-period writing 中心 for nakago is also seen; the older and most common form is 茎.)
Mekugi-ana
The hole (or holes) drilled through the tang for the mekugi, a small bamboo peg that pins the blade into the handle. Additional holes often mean the blade was shortened and remounted over its life, another clue to its history.
Yasurime
The deliberate file marks cut into the tang. They add grip against the handle and, because different schools favored different patterns, they help attribute a blade. This is craft detail, not decoration for its own sake.
The Hamon: The Temper Line
The visible frontier between hard edge and softer body
The hamon is the wavering line that runs above the edge, and it is the signature of differential hardening. Before the final quench the smith coats the blade in clay, thin along the edge and thick over the body. In the quench the thinly coated edge cools fast and hardens into martensite, while the thickly coated back cools slowly and stays tougher. The hamon is the visible boundary between those two states, brought out later by polishing. It is functional first and beautiful second: the hard edge holds keenness, the soft back absorbs shock.
Hamon are grouped by shape. The names below are standard descriptive terms used in Japanese sword study, including in NBTHK appraisal writing.
Suguha
A straight, even temper line with little undulation. Deceptively demanding to execute cleanly.
Midare
An irregular, undulating hamon. A broad family that contains most of the patterned temper lines below.
Notare
Wide, gentle, rolling waves, like a slow swell on water.
Gunome
A repeating pattern of rounded, roughly even humps, often likened to a row of half-circles.
Choji
A pattern of shapes said to resemble cloves, with rounded heads on narrower necks. Associated with several classic schools.
A note on hataraki
Within and around the hamon are fine activities the Japanese call hataraki, such as nie and nioi, bright crystalline effects that a polisher reveals. Describing them precisely is a specialist skill, and reputable references are careful not to overstate what a given effect proves. We name them here so the terms are familiar, without claiming to settle debates that experts still have.
The Grain and the Groove
Hada, the folded-steel grain, and hi, the fuller cut into the blade
Hada
The surface pattern left by repeatedly folding and forge-welding the steel. It is revealed by polishing and reads like wood grain in metal.
Itame
A grain resembling the irregular figure of sawn planks. One of the most common hada types.
Mokume
Concentric, swirling figure like a wood burl or knot. Often appears mixed with itame.
Masame
A straight, parallel grain running along the blade. Strongly associated with the Yamato tradition of present-day Nara.
Bo-hi
A long straight fuller ground into the flat of the blade. It lightens the sword and shifts balance; it is not a "blood groove," a popular but unsupported label. Hi come in several forms beyond the single bo-hi.
Sori: The Curve
How the blade bends, and where the deepest point of the curve sits
Sori is the curvature of the blade, measured as the gap between the spine and a straight line drawn from the notch at the tang to the tip. Much of the curve appears during the quench, as the differentially hardened edge and body cool at different rates and the blade springs into shape. Where the deepest point of the curve falls is itself a named feature and a clue to a blade's age and school.
Koshi-zori
The deepest point of the curve sits nearer the tang, toward the waist of the blade. It is characteristic of earlier tachi, dominant from the Heian into the early Kamakura period.
Torii-zori
Also called naka-zori. The deepest point of the curve sits near the middle of the blade, echoing the lintel of a torii gate. This is the most common form on Japanese swords overall.
Saki-zori
The deepest point of the curve sits nearer the tip. It is frequently seen on later uchigatana of the Edo period and can aid a cutting draw.
Uchizori
A slight curve the opposite way, toward the edge side rather than the spine. It is seen mainly on tanto and armor-piercing blades, where it helps control the tip in a thrust.
Why a kitchen knife is (mostly) straight
The sword's curve serves a slicing draw cut on a moving target. A kitchen knife works against a fixed board, so most Japanese kitchen profiles are far flatter, with only a gentle belly toward the tip for rocking. The shared idea is not the amount of curve but the reason for it: geometry follows the cut the tool is meant to make.
The Mounting: Koshirae
The fittings that turn a bare blade into a wearable sword
A finished blade is only part of a sword. The koshirae is the full set of mountings, the handle, guard, collar, and scabbard, along with the small fittings that dress them. A working mount had to be secure and comfortable; a formal one could also be a showcase of metalwork. Below are the principal pieces.
Tsuka
The grip. Built over a wooden core that fits the tang, it is dressed with rayskin and a cord wrap and secured to the blade by the bamboo mekugi peg. Everything below is mounted onto or around the tsuka.
Samegawa
The panel of ray (or shark) skin wrapped over the wooden handle core beneath the cord. Its hard, pebbled surface grips the overlying wrap and keeps it from sliding.
Tsuka-ito
The cord, usually silk or cotton and sometimes leather, wrapped over the samegawa in a crossing pattern. It provides grip, secures the menuki, and is one of the most visible elements of the mount.
Menuki
A small pair of ornaments set under the handle wrap, usually one on each side. They are decorative but also sit under the palm and hand, helping seat the grip.
Fuchi and Kashira
A matched pair: the fuchi is the collar at the guard end of the handle, and the kashira is the cap at the butt end. Together they reinforce the tsuka and are often crafted as a set.
Tsuba
The guard between handle and blade. It keeps the hand from sliding onto the edge and balances the sword. Tsuba became an art form in their own right, ranging from plain iron to elaborate inlaid metalwork.
Habaki
A wedge-shaped metal collar fitted at the machi notches. It locks the blade snugly into the scabbard, takes the strain off the fittings, and centers the blade in the mount. Nearly every Japanese sword has one.
Saya
The scabbard, traditionally carved from lightweight wood (often ho, magnolia) in two halves and finished with lacquer. Magnolia is chosen because it is gentle on the polished edge, the same wood favored for many Japanese knife handles and knife sheaths.
From This Blade to Your Board
What the sword's anatomy shares, honestly, with a kitchen knife
It would be easy to overstate the link, so here is the honest version. A kitchen knife is not a small sword, and most of the sword's mounting has no kitchen equivalent. What genuinely carries over is the logic of the steel and the edge. Differential treatment of a hard cutting edge over a tougher body, the reading of grain in folded or clad steel, the shinogi ridge on a single-bevel blade, the choice of magnolia because it is kind to a keen edge: these are sword ideas that a knife smith uses every day.
That is the thread this whole section follows. The same charcoal-fire craft that shaped these blades was redirected, after the sword left daily life, into the knives a cook reaches for. If you want the kitchen side of the same vocabulary, spine and edge and bevel and grind, our companion page walks the anatomy of a Japanese knife in the same way this one walks the sword.
The kitchen counterpart
See the same parts named on a cook's blade in Anatomy of a Japanese Knife.
Frequently Asked
What is the single most important part of a katana to a collector?
The nakago, the tang. Because it is rarely reworked, its shape, patina, file marks, and any signature carry the strongest evidence of a blade's age and maker. Experienced appraisers often study the tang before the polished blade.
What actually causes the hamon?
Differential hardening. The smith coats the blade in clay, thin at the edge and thick over the body, then quenches it. The edge cools fast and hardens while the body stays softer, and the hamon is the visible boundary between the two, revealed by polishing. It is functional, not merely decorative.
Is the groove in the blade a "blood groove"?
No. The groove is a hi, or fuller, and it exists to lighten the blade and adjust its balance and stiffness, the same reason fullers appear on other blades worldwide. The dramatic "blood groove" name is popular but not supported by how the feature is understood in Japanese sword study.
What is the yokote and why does it matter?
The yokote is the short line dividing the tip (kissaki) from the body of the blade. A crisp, correctly placed yokote is a sign of proper geometry and skilled polishing; when it is blurred or absent, it usually points to wear or a poor reshaping.
What is the difference between koshirae and the blade itself?
The blade is the forged and polished steel. The koshirae is the full set of mountings around it, the handle, guard, collar, and scabbard with their fittings. A single blade can be remounted many times over its life, so blade and koshirae are studied as related but separate things.
Further Reading
The Same Heritage, In Your Kitchen
We do not sell swords. We carry the forging tradition that shaped them forward into knives built for the board. Our Premium Damascus chef knife sets a hard cutting core inside layered steel, the same hard-over-tough logic that gave a sword its edge and its spine.
See the Premium Damascus Chef Knife