Symptoms, Syndromes & Pathologies. What’s the difference?


In the biomedical literature a lot of terms are commonly used to describe a variety of diseases, disorders, syndromes and more. Even though broad definitions for all these terms exist, they are usually vague and can often contradict one another. On this resource we will try to give a precise definition, one that we use at Reckonect, in order to streamline their comprehensions, especially in the context of our products.

Keep in mind that these definitions and descriptions are not official but merely a way to try to decipher the meaning of each term in their biological, biochemical and physiological context.


Multiple biomedical terms need to be defined. In order to address each of them in a coherent order, we will first describe the discret terms and thereafter go into the broader one, often interconnected.

First we will start with defect and deficiency, then we’ll define a symptom versus a sign and their combination into a syndrome. This will lead us into the definition of a disease and all the terms assimilated or associated with it: disorder, condition, injury.


The first term we will describe is the biomedical term “defect”.

In medicine, the term defect is often defined as a flaw or an imperfection (1). It is usually regarded as happening at birth (birth defect) and can affect chromosomes, metabolism or structure/anatomy of the body. A birth defect could also results from infection or from intoxication (like fetal alcoholism).

This term is mostly straight forward in its definition.*

Its reference is C1457869 in UMLS.


This term conveys two main idea:

  • A “deficiency” usually refers to a lack or a shortage. In medicine, it is defined as “a shortage of a substance (such as a vitamin or mineral) needed by the body” (2). According to Wikipedia, it is “a lack or a shortage of a functional entity, by less than normal or necessary supply or function” (3). For example an iron deficiency in the blood that could provoke an anemia.
  • It could also mean that a function or structural/anatomical part of the body is not functioning as it is supposed to, that it is deficient.

A deficiency could translate into a condition, a disorder or a disease.

Its reference are C0011155 in UMLS and Q000172 in MeSH.


It starts to get a little complicated with the term “Symptom”. A symptom is a physical or mental feature which is regarded as indicating of a condition of disease, particularly such a feature that is apparent to the patient. Another definition states that it is a subjective evidence of diseases or physical disturbance (4) or that it is caused by a particular disease (5).

The consequence of the disease implying a direct involvement in the appearance of symptoms is still subject to debate. Therefore our own definition will be that a symptom is a perceptible or observable phenomenon or character that could be linked to a state or a disease that it allows to detect, of which it is the sign. An example as a symptom would therefore be a headache.

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Its reference are C1457887 and C0037088 in UMLS and D012816 in MeSH.


The distinction between a sign and a symptom can be tricky. According to scientific literature (6), when physicians are asked about the difference, they would mostly reply in this fashion:

“A symptom is a manifestation of disease apparent to the patient himself, while a sign is a manifestation of disease that the physician perceives. The sign is objective evidence of disease; a symptom, subjective. Symptoms represent the complaints of the patient, and if severe, they drive him to the doctor’s office. If not severe, they may come to light only after suitable questions. The patient perceives, for example, subjective pains and discomforts [Doctor, I have a bad headache], or disturbances of function [Doctor, I can’t move my arm the way I used to], or some simple appearance [Doctor, I have had this rash for the past ten days and I’m worried about it].”

The main difference between a sign and a symptom is that a sign will necessarily “points” to something else (a sign is always of something, that can be quite specific), it will refers to something other than itself. On the other hand, a symptom can stand by itself, it does not need to “point” to anything. Signs, along with symptoms, assist in formulating diagnostic hypothesis.

On important point is that a sign can also be a symptom. For example a headache would be a symptom for a patient, without any connection to any disease, by itself, whereas it will be a sign for the physician who will be able to deduct the disease based on his/her acquired medical knowledge. Thus, a sign has a traditional connection with physicians rather than patients.

Hence, the definition we adopted is as stated on Wikipedia (7): a medical sign is an objective observable indication of a disease, injury, or abnormal physiological state that may be detected during a physical examination, examining the patient history, or diagnostic procedure.

Its reference are C0037088 in UMLS and D012816 in MeSH.


The term syndrome is more straightforward. It is an association of symptoms or signs in a cohesive, correlated and characteristic way, constituting a particular disease or disorder (8).

As an example Turner Syndrome is characterized by the absence of a part or all of one of the sex chromosomes. Signs and symptoms include short stature, webbing of neck, low-set ears, hypogonadism, and sterility.

Its reference are C0039082 in UMLS and D013577 in MeSH.


The main definition of a disorder is the following: a disturbance of a normally functioning body or mind.

A disorder can be mental, physical, structural, genetic, emotional, behavioral and functional. For example, it could be used to identify physical disorder not caused by infectious organisms (metabolic disorder) or to acknowledge the interaction of multiple factors in psychiatric conditions. A known example of mental disorder is schizophrenia.

Often the term disorder is considered more neutral and less stigmatizing than disease or illness and is therefore used instead. Still, there is a subtle difference: A disease would be distinct and measurable whereas a disorder might indicate a possible disease without enough clinical evidence for diagnosis.

Disorder has no reference in UMLS or MeSH.


A condition englobes a variety of terms. It could be a disease, a disorder or a syndrome, and in a broader sense, it is a health problem with certain characteristics or symptoms (9). Thus, a condition indicates a state of health, or rather an abnormal state of health that interferes with the usual feeling of wellbeing. A good example of a condition would be hypersensitivity: the disposition to develop an allergic or pseudoallergic reaction.

Its reference are C0348080 in UMLS and D013568 in MeSH.


The usual definition for injury would be any physiological damage to the body, caused by immediate physical stress. Sometimes this definition is intertwined with the definition of disease or condition (for example certaines knees-related conditions could be defined as injuries).

Injuries can occur in any part of the body and be associated with different symptoms.

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Its reference are C3263723 in UMLS and D014947 in MeSH.


A simple definition for a disease would be “an illness or sickness characterized by specific signs or symptoms” (10). According to the British Medical Journal from 1900, a disease is resulting from pathophysiological response to external and internal factors (11).

Therefore a disease is a medical condition which disrupts the normal functioning and physiological processes of the body, its homeostasis.

  • Illness and Sickness

The terms illness or sickness are usually used as synonyms for disease. However “illness/sickness” is sometimes used to refer specifically of the patient’s personal experience of his/her disease, therefore it is possible for a person to have a disease but to not feel ill, or to be ill without being diseased (for example feeling unwell from emotional stress).

  • Pathology

Pathology is the study of the causes and effects of disease and injury (12). “A pathology” is also a synonym of disease, commonly used by physicians in scientific literature (rather than disease).

Its reference are C0012634 in UMLS and D004194 in MeSH.


  6. King, L. S. Signs and Symptoms. JAMA. 206(5):1063–1065 (1968). doi:10.1001/jama.1968.03150050051011
  8. The British Medical Association Illustrated Medical Dictionary. London: Dorling Kindersley. 2002. pp. 177, 536.
  11. Br Med J 1900;2:1703. doi:10.1136/bmj.2.2085.1703
  12. Cross, S. Underwood’s pathology : a clinical approach. (1942).