Thickness:
The standard for examining the thickness of the tongue is whether it is "bottom visible" or "bottom invisible". That means the tongue fur with dimly visible body of the tongue is thin fur, while the tongue fur with invisible body of the tongue is thick fur.

The thickness of the tongue fur reflects the degree and severity of the pathogenic factors as well as the development of disease. Generally speaking, thin tongue fur is seen at the primary stage of exogenous disease, suggesting that the pathogenic factors are superficial and the disease is mild; it is also seen in diseases due to internal impairment with deficiency of healthy qi, especially with hypofunction of the spleen and stomach. Thick tongue fur is the sign of exuberance of pathogenic factors, frequently due to internal invasion of exogenous pathogenic factors, or due to internal stagnation of phlegm, dampness and food retention as well as fumigation of gastric qi with turbid substance and pathogenic factors.  

During the course of a disease, the change of the tongue fur from thinness to thickness indicates gradual exuberance of pathogenic factors, development of pathogenic factors from the exterior to the interior and progress of  pathological conditions from mildness to severity; the change of the tongue fur from thickness to thinness suggests predomination of healthy qi over pathogenic factors, elimination of pathogenic factors internally and externally as well as development of the pathological conditions from severity to mildness.

Moistening and dryness of tongue fur:
The tongue fur that is moist with moderate dampness is called moist tongue fur. The tongue fur with excessive dampness and slipperiness is called slippery tongue fur. The tongue fur that is dry, without fluid or even fissured is called dry tongue fur. The tongue fur that is dry, rough and sandy is called rough tongue fur.

The moistening and dryness of the tongue fur reflect the conditions and distribution of body fluid. Moist tongue fur indicates sufficiency and upward distribution of body fluid. Slippery tongue fur indicates cold-dampness or retention of fluid and internal invasion of cold-dampness, or asthenia of yangqi and failure of qi to transform fluid. Dry and rough tongue fur indicates consumption of fluid by exuberant heat or consumption of yin fluid. The drier and rougher the tongue fur is, the severer the consumption of body fluid. Such a condition is usually seen at the medium and advanced stages of exogenous febrile diseases. Besides, internal stagnation of pathogenic dampness, obstruction of yangqi or asthenia of yangqi and failure of qi to transform fluid may also lead to dry tongue fur, the manifestation of which is light-whitish tongue accompanied by chest oppression and dry mouth without desire to drink.

During the course of a disease, the change of the tongue fur from moisture to dryness indicates consumption of body fluid and severity of heat, while the change of tongue fur from dryness to moisture suggests abatement of pathogenic heat and gradual restoration of body fluid.

Greasy and putrid tongue fur:
Tongue fur compact and difficult to exfoliate which is thick on the center and thin on the margins is called greasy tongue fur. While the tongue fur loose, sparse and easy to exfoliate with thickness on both the center and margins is called putrid tongue fur.
 
The greasiness and putridity of the tongue fur reflect the decline and development of yangqi and turbid dampness. Greasy tongue fur is usually caused by internal exuberance of dampness and obstruction of yangqi, often seen in syndromes due to dampness, phlegm, retention of food and damp-febrile factors. Putrid tongue fur is usually caused by fumigation of excess of yang-heat, often seen in syndromes due to retention of food in the stomach and intestines or accumulation of phlegm and turbid substance.
                                
Exfoliating tongue fur:
Exfoliating tongue fur means that the fur on the tongue has exfoliated partially or completely during the course of a disease. Partial exfoliation of tongue fur is divided into anterior exfoliated tongue fur, medium exfoliated tongue fur and patched exfoliated tongue fur. If the tongue fur is completely exfoliated, it is called mirror-like tongue. Exfoliation of the tongue fur is usually due to failure of deficient gastric qi to fumigate the tongue or due to failure of the exhausted gastric yin to moisten the tongue. Therefore the exfoliations of the tongue fur can tell whether the gastric qi and yin still exist or not and how the prognosis of a disease will be.

Exfoliated tongue fur and deep-red tongue indicate consumption of yin by exuberant heat; exfoliated tongue fur and light-colored tongue indicate consumption of both qi and yin; mirror-like tongue suggests severe consumption of gastric qi and is a sign of the exhaustion of gastric yin. If the tongue fur is patched and greasy, it suggests that phlegm is not resolved, healthy qi is consumed and the pathological conditions are complicated. During the course of a disease, if the tongue fur is completely exfoliated, it means insufficiency of gastric qi and yin, gradual decline of healthy qi and gradual worsening of the pathological conditions; if the tongue fur reappears thin and white after exfoliation, it indicates gradual restoration of gastric qi and favorable recovery from the disease.