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Large Formula (Da Fang): One sovereign herb, two minister herbs, nine assistant herbs; this constitutes the specification of a large formula.
Its applications are twofold: First, when a disease presents with concurrent syndromes and the pathogenic factor is not singular, it cannot be treated with only one or two herbs; such cases are suitable for large formulas. Second, when treating the Kidney and Liver located in the lower jiao (Lower Burner), which are distant from the stomach and intestines, it is appropriate to use larger dosages administered in a single dose.

Small Formula (Xiao Fang): One sovereign herb, two minister herbs, four assistant herbs; this constitutes the specification of a small formula.
Its applications are twofold: First, when a disease lacks concurrent syndromes and the pathogenic factor is singular, it should not be treated with multiple herbs; such cases are suitable for small formulas. Second, when treating the Heart and Lung located in the upper jiao (Upper Burner), which are close to the stomach and intestines, it is appropriate to use smaller dosages administered frequently.

Slow-Acting Formula (Huan Fang): Treatment of the primary condition should be slow; tonification of the upper jiao or treatment of diseases in the upper jiao requires a slow-acting formulation. Whether addressing exterior/interior conditions, inducing sweating, or purging, there are situations requiring slowness. A slow action implies thin qi and flavor; substances with thin qi and flavor should be taken in small amounts but frequently.
Its applications are fivefold: 1) Using sweet herbs to induce slowness, such as sugar, honey, dates, Malva verticillata seeds, and Glycyrrhizae Radix et Rhizoma (Licorice Root), taking advantage of their ability to linger in the diaphragm. 2) Using pills to induce slowness, as pill formulations act more slowly than decoctions or powders. 3) Formulas with numerous ingredients, where the multitude of herbs prevents any single herb from exerting its full potency rapidly. 4) Formulas using non-toxic herbs to treat disease, where the absence of toxicity naturally results in a slower attack on the pathogen. 5) Formulas with thin qi and flavor, where the subtle nature of the herbs leads to a gentle effect.

Urgent Formula (Ji Fang): Treatment of exogenous pathogens should be urgent; tonification of the lower jiao or treatment of diseases in the lower jiao requires an urgent formulation. Whether addressing exterior/interior conditions, inducing sweating, or purging, there are situations requiring urgency. An urgent action implies strong qi and flavor; substances with strong qi and flavor should be taken in large amounts in a single dose.
Its applications are fourfold: 1) Urgent purgation for excessive heat, indicated by dryness, constipation of both bowels, delirium, and mania, requiring immediate purgation. 2) Urgent cleansing for wind invasion, indicated by stroke with locked jaw and loss of consciousness, requiring immediate cleansing. 3) Emergency treatment for drug toxicity, where toxic herbs act swiftly; administration induces vomiting or diarrhea to rapidly overcome the severe pathological trend. 4) Formulas with strong qi and flavor, where the potent nature of the herbs leads to an urgent effect.

Odd Formula (Qi Fang): One sovereign herb, two minister herbs; this constitutes the specification of an odd formula. Diseases located proximally or inferiorly are treated with odd formulas. All conditions in the Yang aspect are treated with odd formulas.
Its applications are twofold: 1) Odd formulas with single-natured herbs, such as Du Shen Tang (Single Ginseng Decoction). 2) Cases where the pathology suits an odd formula, defined as one sovereign and two ministers, or two sovereigns and three ministers. These numbers align with Yang; thus, they are suitable for purgation rather than inducing sweating. (Wang Andao stated: Odd formulas have weak power. When purgation is indicated, an odd formula is suitable because purgation is inherently easier to execute. Using an even formula would result in excessive internal attack.)

Even Formula (Ou Fang): Two sovereign herbs, four minister herbs; this constitutes the specification of an even formula. Diseases located distally or those requiring induced sweating are treated with even formulas. All conditions in the Yin aspect are treated with even formulas.
Its applications are threefold: 1) Even formulas composed of paired herbs, such as Chen Fu Tang (Cyperus and Aconite Decoction). 2) Even formulas formed by combining two prescriptions, such as Wei Ling Tang (Stomach and Five Herbs Decoction). 3) Cases where distant pathology suits an even formula, defined as two sovereigns and four ministers, or four sovereigns and six ministers. These numbers align with Yin; thus, they are suitable for inducing sweating rather than purgation. (Wang Andao stated: Even formulas have balanced and substantial power. When sweating is indicated, an even formula is suitable because sweating can be difficult to achieve. Using an odd formula would cause the medicinal qi to disperse outwardly, resulting in insufficient power.)

Both Odd and Even formulas involve odd/even characteristics in terms of taste and numerical composition, which must be carefully examined to avoid violating principles of cold and warmth.
The Yang aspect of Heaven corresponds to Odd. For example, Sheng Ma Tang (Cimicifugae Decoction) ascends without descending, hence it is called an Odd formula, as it acts in the realm of Heaven.
Sweating originates from the depths of Earth (Nine Earths). To ascend from Earth to Heaven, bitter flavors are needed to reach the depths, and warm properties are needed to reach the heights. Therefore, bitter-warm agents are used to rise from Nine Earths to Nine Heavens, making it an Even formula.
The Yin aspect of Earth corresponds to Even. For example, Tiao Wei Cheng Qi Tang (Regulate the Stomach and Order the Qi Decoction) descends without ascending, hence it is called an Even formula, as it acts in the realm of Earth.
Purgation originates from the heights of Heaven (Nine Heavens). To descend from Heaven to Earth, pungent flavors are needed to reach the heights, and cool properties are needed to reach the depths. Therefore, pungent-cool agents are used to guide from Nine Heavens down to the depths of Earth, making it an Odd formula.

Compound Formula (Fu Fang): If an Odd formula fails, apply an Even formula; if an Even formula fails, apply an Odd formula; hence it is called "Fu" (Repeat/Compound). "Fu" means again or repeatedly. Jiegu stated: Ten parts tonification to one part purgation, or several parts purgation to one part tonification, serves to maintain the balance of unblocking and obstructing.
Its applications are twofold: 1) Compounds formed by combining two or three formulas, such as Gui Zhi Er Yue Bi Yi Tang (Two Parts Cinnamon Twig and One Part Ephedra Decoction). 2) Compounds with equal dosages, such as Wei Feng Tang (Wind Protecting Decoction), where all herbs are used in equal proportions. Additionally, "Fu" refers to repetition in combination (combining two or three formulas) and "Fu" refers to alternation (if an Odd formula fails, switch to an Even formula).