Chinese character strokes

Strokes are the smallest structural units making up written Chinese characters. In the act of writing, a stroke is defined as a movement of a writing instrument on a writing material surface, or
the trace left on the surface from a discrete application of the writing implement. The modern sense of discretized strokes first came into being with the clerical script during the Han dynasty. In the regular script that emerged during the Tang dynasty—the most recent major style, highly studied for its aesthetics in East Asian calligraphy—individual strokes are discrete and highly regularized. By contrast, the ancient seal script has line terminals within characters that are often unclear, making them non-trivial to count.
Study and classification of strokes is useful for understanding Chinese character calligraphy, ensuring character legibility, identifying fundamental components of radicals, and implementing support for the writing system on computers.

Evolution

The terminals of the individual marks in ancient character forms are often unclear, and it is sometimes nontrivial to count them. The modern motion of discretized strokes did not fully emerge until clerical script:

Purpose

The study and classification of strokes is used for:

understanding Chinese character calligraphy – the correct method of writing, shape formation and stroke order required for character legibility;
understanding stroke changes according to the style that is in use;
defining stroke naming and counting conventions;
identifying fundamental components of Han radicals; and
their use in computing.
Formation

When writing Han radicals, a single stroke includes all the motions necessary to produce a given part of a character before lifting the writing instrument from the writing surface; thus, a single stroke may have abrupt changes in direction within the line. For example:

is classified as a basic stroke because it is a single stroke that forms a line moving in one direction.
is classified as a compound stroke because it is a single stroke that forms a line that includes one or more abrupt changes in direction. This example is a sequence of three basic strokes written without lifting the writing instrument such as the ink brush from the writing surface.
Direction

All strokes have direction. They are unidirectional and start from one entry point. As such, they are usually not written in the reverse direction by native users. Here are some examples:

Types

strokes are an attempt to identify and classify all single-stroke components that can be used to write Han radicals. There are some thirty distinct types of strokes recognized in Chinese characters, some of which are compound strokes made from basic strokes. The compound strokes comprise more than one movement of the writing instrument, and many of these have no agreed-upon name.

Basic strokes

A basic stroke is a single calligraphic mark moving in one direction across a writing surface. The following table lists a selection of basic strokes divided into two stroke groups: simple and combining. "Simple strokes" can be written alone. "Combining strokes" never occur alone, but must be paired with at least one other stroke forming a compound stroke. Thus, they are not in themselves individual strokes.
Note, the basic stroke Diǎn "Dot" is rarely a real dot. Instead it usually takes the shape of a very small line pointing in one of several directions, and may be long enough to be confused with other strokes.

Compound strokes

A compound stroke is produced when two or more basic strokes are combined in a single stroke written without lifting the writing instrument from the writing surface. The character "eternity", described in more detail in, demonstrates one of these compound strokes. The centre line is a compound stroke that combines three stroke shapes in a single stroke.
;Basics for making compound strokes
In most cases, concatenating basic strokes together form a compound stroke. For example, Vertical / Shù combined with Hook / Gōu produce . A stroke naming convention sums the names of the basic strokes, in the writing order.
An exception to this applies when a stroke makes a strictly right-angle turn in the Simplified Chinese names. Horizontal and Vertical strokes are identified only once when they appear as the first stroke of a compound; any single stroke with successive 90° turns down or to the right are indicated by a Bend 折. For example, an initial Shù followed by an abrupt turn right produces . In the same way, an initial Shù followed by an abrupt turn right followed by a second turn down produces . However, their inherited names are "Vertical–Horizontal" and "Vertical–Horizontal–Vertical". We need not to use "Bend" in the inherited names.
Nearly all complex strokes can be named using this scheme.

Nomenclature

Organization systems used to describe and differentiate strokes may include the use of roman letters, Chinese characters, numbers, or a combination of these devices. Two methods of organizing CJK strokes are by:

Classification schemes that describe strokes by a naming convention or by conformity to a taxonomy; and
Categorization schemes that differentiate strokes by numeric or topical grouping.

In classification schemes, stroke forms are described, assigned a representative character or letterform, and may be arranged in a hierarchy. In categorization schemes, stroke forms are differentiated, sorted and grouped into like categories; categories may be topical, or assigned by a numeric or alpha-numeric nominal number according to a designed numbering scheme.

Pinyin naming convention in Unicode standard

A naming convention is a classification scheme where a controlled vocabulary is used systematically to describe the characteristics of an item. The naming convention for a CJK stroke is derived from the path mark left by the writing instrument. In this instance, the first letter of each stroke component - transliterated with pinyin pronunciation - are concatenated to form a stroke name with the sequence of letters indicating the basic strokes or stroke components used to create the CJK stroke. This system is used in the Unicode standard when encoding CJK stroke characters. In a basic stroke example, H represents the stroke named ; in a compound example, represents .
While no consensus exists, there are up to 12 distinct basic strokes that are identified by a unique radical.

Letter

Stroke direction

Simp./Trad.

Pinyin

Biǎn

Diǎn

Gōu

Héng

Nà

Piě

Quān

Shù

Tí

Wān

Xié

Zhé

Meaning

"Flat"

"Dot"

"Hook"

"Horizontal"

"Right-falling"

"Left-falling"

"Circle"

"Vertical"

"Rising"

"Curved"

"Slant"

"Bent"

There are many CJK compound strokes, however there is no consensus for sequence letter naming of compound strokes using the basic strokes. The following table demonstrates one of the CJK stroke naming convention:

Stroke	Name in PRC	Abbr	Full Name	Dictionary meaning and Note	Example characters	Encoding
	横	H	Héng	yī, "cardinal number one", "alone".	二三丁丞丈世不上十卅七	U+31D0
	提	T	Tí		冰淋病孑治冶冽暴氾录地虫	U+31C0
	横钩	HG	Héng Gōu	wān, ya, zhé turning stroke / to break.	疋了危予矛子字令疏写冖	U+31D6
	横撇	HP	Héng Piě		又水夕径炙双叒今	U+31C7
	横折	HZ	Héng Zhé		口囗己田品吕申甲圆巪	U+31D5
	横折钩	HZG	Héng Zhé Gōu	.	羽习包勻葡用青甫勺月也乜	U+31C6
	横折提	HZT	Héng Zhé Tí		讠计鳩	U+31CA
	横折折	HZZ	Héng Zhé Zhé		凹	U+31C5
	横折弯	HZW	Héng Zhé Wān		殳投朵	U+31CD
	横折弯钩	HZWG	Héng Zhé Wān Gōu	Unofficial name "HWG" is used by Hugo Lopez to refer to both HZWG and HXG.	九几丸杂	U+31C8
	横斜钩	HXG	Héng Xié Gōu	This stroke was merged into stroke HZWG in Unicode., but later disunified.	飞风瘋凬虱迅气	U+31E4
	横斜弯钩	HXWG	Héng Xié Wān Gōu	yǐ, niè, "the second of the ten heavenly stems", "second"; zhé turning stroke / to break.	氹乞乤艺	U+31E0
	横折折折	HZZZ	Héng Zhé Zhé Zhé		凸	U+31CE
	横折折撇	HZZP	Héng Zhé Zhé Piě		建及	U+31CB
	横撇弯钩	HPWG	Héng Piě Wān Gōu		阝队邮	U+31CC
	横折折折钩	HZZZG	Héng Zhé Zhé Zhé Gōu	nǎi, archaic form of "then", "really, indeed", "namely", "you, your".	乃孕仍	U+31E1
	竖	S	Shù	gě, gǔn, "vertical line".	丩中串讧乍上五丑	U+31D1
	竖钩	SG	Shù Gōu	jué, "a vertical line with a hook".	爭事求水	U+31DA
	竖提	ST	Shù Tí		以比切卯食良艮很狠鄉民	U+31D9
	竖折	SZ	Shù Zhé		断陋继山互彙牙乐东	U+31D7
	竖弯	SW	Shù Wān		區亡妄四	U+31C4
	竖弯左	SWZ	Shù Wān Zuǒ		肅嘯蕭簫	U+31D8
	竖弯钩	SWG	Shù Wān Gōu	yǐn, "hidden", "mysterious", "small", usually read as / yǐn.	乱己已巳	U+31DF
	竖折折	SZZ	Shù Zhé Zhé		亞鼎卐吳	U+31DE
	竖折撇	SZP	Shù Zhé Piě	This stroke was merged into stroke SZZ in Unicode., but later disunified.	专 ? ? ?	U+31E5
	竖折弯钩	SZWG	Shù Zhé Wān Gōu		亏强弓丏丐与马鸟丂号	U+31C9
	撇	P	Piě	usually read as 撇 piě, "line", "slash".	乂爻禾毛乏乖釆衣八行	U+31D2
	竖撇	SP	Shù Piě		乃月用齊几人班大	U+31D3
	撇钩	PG	Piě Gōu		乄	U+31E2
	撇折	PZ	Piě Zhé		弘玄公厶翁	U+31DC
	撇点	PD	Piě Diǎn	quǎn, a little drain between fields, usually read as quǎn.	女巛巡獵災甾	U+31DB
	点	D	Diǎn	zhǔ, "dot", usually read as 點 / 点 diǎn.	丸叉义永冰凡丹主求火刃	U+31D4
	捺	N	Nà	㇏ usually read as 捺 nà.	大人天入走边廷尺	U+31CF
	提捺	TN	Tí Nà	fú, "stretch". yí, "to move".	尐之道八入廻	U+31DD
	斜钩	XG	Xié Gōu		戈弋戰我	U+31C2
	扁斜钩	BXG	Biǎn Xié Gōu		心必沁惢蕊	U+31C3
	弯钩	WG	Wān Gōu		狐狱豹家啄嶽貓家逐	U+31C1
	圈	Q	Quān	líng, "zero"; also read as quān, "circle". Rare.	〇㔔㪳㫈	U+31E3

Besides, some strokes have been unified or abandoned in Unicode:

Stroke	Name in PRC	Abbr	Full Name	Note	Example characters
	横撇弯	HPW	Héng Piě Wān	It only appears in Regular script, can be merged into stroke HPHP in Song typeface.	辶过边
	竖折折弯钩	SZZWG	Shù Zhé Zhé Wān Gōu	This stroke has been merged into stroke SZZG in Unicode.	弓丐
	弯	W	Wān	It never occurs alone, only appears inside compound strokes.	辶豕 ?
	弯钩	WG	Wān Gōu	It never occurs alone, only appears inside compound strokes.	乙
	点捺	DN	Diǎn Nà	This stroke has been merged into stroke N in Unicode.	內全廴
	平捺	PN	Píng Nà	This stroke has been merged into stroke N in Unicode.	是走廴
	提平捺	TPN	Tí Píng Nà	This stroke has been merged into stroke TN in Unicode.	辶之辷

Note that some names in the list do not follow the rules of controlled vocabulary. For example, stroke P '' is not found in the compound stroke PN. The name "PN" comes from 平捺, not 撇捺. The meaning of 平 is "flat", and it should be called "BN" 扁捺 if the rules are to be followed closely. The letter "Z" in stroke SWZ means 左, not 折. The meaning of 左 is "left", and it is not defined in the naming convention. Moreover, some 折 strokes are far more than or far less than 90°, such as stroke HZZZG, stroke HZZP and stroke PZ.
Some strokes are not included in the Unicode standard, such as,,,,,, etc.
In Simplified Chinese, stroke TN is usually written as .