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The form of the pulse is long and round, like water passing through the center of a scallion leaf. It varies in length (Chang) and shortness (Duan), largeness (Da) and smallness (Xiao), emptiness (Xu) and fullness (Shi), slackness (Huan) and tension (Jin). (Length and shortness refer to the longitudinal extent; largeness and smallness refer to the transverse width; emptiness and fullness refer to the accumulation or lack of internal substance; slackness and tension refer to the relaxation or constriction of the vessel.)

Long: The pulse extends beyond the three finger widths (Cun, Guan, Chi) is called Long.
Short: The pulse does not fill the space of the three finger widths is called Short.
When palpating the Cun Kou (Inch Gate) pulse, it runs from the chest to the tip of the thumb without interruption, so originally there is no concept of length or shortness. However, some pulses manifest visibly, while others do not. Those that do not manifest fully are felt only within the three-finger span upon pressure; those that manifest fully extend beyond the three fingers. Thus, length and shortness must be distinguished. (Gao Gufeng stated: There is physical length and dynamic length. Dynamic length refers to a lingering resonance in the pulse's arrival. Gao's explanation is excellent. Although length and shortness primarily describe physical form, any pulse considered precious for its spirit and prolonged vitality can be envisioned through this description.)

Large: A pulse that is large and vigorous at the superficial level (Floating/Fu) is called Hong (Surging). A pulse that is large and diffuse, lacking clear boundaries between the pulse and the flesh, is called San (Scattered).
Small: Opposite to Large, also known as Xi (Fine). When extremely fine and forceless, it is called Wei (Minute).
Empty (Xu): Xu means not solid. When extremely empty with a hollow center, it is called Kou (Bamboo Shoot).
Full (Shi): Shi means solid or knotty. Feeling a Shi pulse is like pressing a pig tendon; feeling a Xu pulse is like pressing a rush pith; feeling a Kou pulse is like pressing a scallion stalk. Old texts state that strength at floating, middle, and deep levels indicates Shi (Full); weakness at all three indicates Xu (Empty); strength at floating and deep but weakness at the middle indicates Kou. While not incorrect, this is not the definitive explanation. (A Shi pulse is like a scallion filled with water; a Xu pulse lacks this filling; a Kou pulse is even less filled.)

Slack (Huan): Means soft and relaxed. If excessively so, it becomes Ruannuo (Soft and Weak). Historically, Huan was sometimes grouped with Chi (Slow) because Huan encompasses two meanings.
Tension (Jin): Means rapid and tense, opposite to Huan. It feels like a tightened bowstring or a pulled rope, rigid and resisting the finger. If the tension is not severe, it is called Xian (Wiry). If Xian or Jin is also large, it is called Ge (Drum Skin) or Lao (Deep-Fixed).

Some variations in length are constitutional. Individuals with prominent tendons may have longer pulses; those without prominent tendons may have shorter pulses. Some vary with seasons: Spring pulses are long, Autumn pulses are short. Some vary with disease: Excess pathogenic factors lead to long pulses; deficiency of healthy Qi leads to short pulses.

Some variations in size are constitutional, known as Liu Yang (Six Yang) and Liu Yin (Six Yin) pulses. (Those born with large pulses are Liu Yang; those with small pulses are Liu Yin.) Some vary with seasons: Pulses enlarge during growth seasons and shrink during收敛 (convergence/storage) seasons. Some vary with disease: Excess pathogens cause large pulses (pathogenic qi stagnation); deficiency of healthy Qi causes small pulses (decline of blood and qi).

Variations in emptiness/fullness can also be constitutional. Those with firm flesh often have Full pulses; those with soft flesh often have Empty pulses. They also vary with seasons: In Spring and Summer, when qi exerts outwardly, pulses may appear large but show signs of emptiness; in Autumn and Winter, when qi stores inwardly, pulses may appear small but show signs of fullness. Pathologically, a large and full pulse (stagnation and accumulation) versus a small and empty pulse (decline and hollowness) helps identify whether the disease is dominated by excess pathogens or deficient healthy Qi (both excess indicate pathogen excess; both deficiency indicate healthy Qi deficiency). A large but empty pulse (excess qi, deficient blood, like blowing air into an empty scallion tube) versus a small but full pulse (blood is sufficient, but qi is too weak to propel) helps identify Yin-Yang imbalance.

Variations in tension/slackness can be constitutional. Those with tight skin often have Tense pulses; those with loose skin often have Slack pulses. Seasonal variations occur due to cold causing contraction and heat causing relaxation. Pathological variations include external Wind-Cold or internal injury from cold/raw food, where Cold excess causes contraction, resulting in a Tense, forceful pulse. Heat or Dampness causes relaxation, resulting in a Soft, forceless pulse.

Appendix: Hong, San, Wei, Kou, Xian, Ge, Lao, Ruan, Ruo pulses.

Hong: Hong simply means large. Old texts described it as "strong arrival, weak departure," referring to its vigor at the superficial level.
San: The pulse shape should be gathered and round, but now it is diffuse and uncontained. It seems large but is not truly large; it represents extreme emptiness scattering outward.
Wei: Ancient texts associated Wei with Floating and Xi with Deep. They distinguished Wei as Yang deficiency and Xi as Blood deficiency. This collection defines pulses by their primary meaning, so Wei is defined as extremely fine and forceless.
Kou: A pulse that is empty and hollow in the center. "Kou" is the name for a specific type of scallion. It feels like lying a scallion tube under the finger: present on light and heavy pressure, but absent on medium pressure. This is a pulse of blood loss.
Xian: Similar to Jin but slightly less intense. It merely needs to show some resistance to the finger, unlike Jin which beats against the palm. Xian or Jin pulses caused by external pathogens are easier to treat; those caused by healthy Qi deficiency are difficult to cure. This is because Spleen-Stomach failure transforms harmonious Qi into rigidity ("Earth fails, Wood attacks"), which is incurable. Sometimes ancients equated Chang (Long) with Xian, describing Spring pulses as soft, straight, and long. Now distinguished, Xian implies urgency and rigidity, not just length.

Ge and Lao: Ge is Xian, large, slow, floating, and empty, feeling like pressing a drum skin (hollow inside, tight outside). Lao is Xian, large, slow, deep, and solid, indicating deeply entrenched Cold pathogens, like a prison.

Ruan and Ruo: Both represent extreme softness and slackness with a lack of force. Old texts associated Ruan with Floating and Ruo with Deep.