"Root" (本) refers to the fundamental essence of life, including the spirit, original qi, zang-fu organs, qi and blood, body fluids, and other physiological and psychological qualities and activities crucial to human life and survival. "Deficiency in Root" indicates that these essential aspects of survival are insufficient or depleted.

"Manifestation" (標) refers to the manifestations or symptoms of disease. "Excess in Manifestation" signifies that these manifestations are exuberant, overwhelming, or difficult to subdue. For example, due to the invasion of pathogenic qi such as wind-cold or viruses and bacteria, severe symptoms like intense cough, sore throat, headache, fever, etc., may arise. Alternatively, chronic sexually transmitted diseases may lead to symptoms such as limb edema, abdominal distension and fullness, or chest fullness and rapid breathing, presenting a robust physical appearance.

Suwen-Tongping Xushi Lun clearly explains the meanings of deficiency and excess: "Exuberance of pathogen causing excess syndrome; lack of essential qi causing deficiency syndrome." "Excess" refers to the exuberant and robust symptomatic manifestations caused by pathogenic qi, while "deficiency" refers to the state where the patient's spirit and original qi are depleted. This is the most classical description of "deficiency in root and excess in manifestation."

Clinically, those with "deficiency in root" do not necessarily exhibit "excess in manifestation," and those with "excess in manifestation" do not necessarily indicate "deficiency in root." However, these two conditions are often coupled. Suwen-Ping Rebing Lun states, "invasion of pathogen must be due to deficiency of essential qi," meaning that pathogenic qi such as wind-cold or viruses and bacteria are more likely to invade when the body's healthy qi is weak. Suwen-Cifa Lun also says, "When healthy qi is preserved within, pathogenic qi cannot interfere," meaning that as long as the body's spirit and original qi are sufficient, various pathogenic qi are less likely to invade.

Once pathogenic qi invades a person with a deficient constitution, due to the host's weak defenses, the pathogenic qi can move with less resistance, replicate more extensively, and cause greater damage, making the symptoms appear more severe. Conversely, when a person with a deficient constitution falls ill, due to their weak body and poor recovery ability, the symptoms are usually more severe and prolonged compared to those with a healthy constitution. Thus, "deficiency in root" can easily lead to "excess in manifestation," and "excess in manifestation" often reveals "deficiency in root."