Bilingual English–French glossary: 40 key terms

ME/CFS, exertion and fatigue

1. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) — encéphalomyélite myalgique / syndrome de fatigue chronique (EM/SFC)

A complex, chronic illness affecting multiple body systems ^[1]. According to the IOM/NAM criteria as presented by the CDC, it combines a substantial reduction in prior functioning accompanied by fatigue, post-exertional malaise and unrefreshing sleep, together with cognitive difficulties and/or orthostatic intolerance ^[2]. See ME/CFS and post-exertional malaise.

2. Post-exertional malaise (PEM) — malaise post-effort

A worsening of symptoms that can follow minimal cognitive, physical, emotional or social activity, or activity that was previously tolerated; it typically occurs 12 to 48 hours after the activity and can last for days or even weeks ^[1]. See ME/CFS and post-exertional malaise.

3. Post-exertional symptom exacerbation (PESE) — exacerbation des symptômes après effort

Another name for post-exertional malaise, according to NICE ^[1]. Use of this term does not, on its own, mean that the criteria for ME/CFS are met.

4. Fatigue — fatigue

A symptom of lack of energy or exhaustion, present in many diseases and non-specific. In ME/CFS, NICE describes fatigue with several components (flu-like feeling, “wired but tired”, lack of energy, cognitive fatigue, rapid loss of strength after starting an activity), distinct from post-exertional malaise, which is listed separately in the criteria ^[1].

5. Unrefreshing sleep — sommeil non réparateur

Sleep that does not bring a sense of recovery: even after a full night, the person does not feel rested ^{[1, 2]}.

6. Energy management (pacing) — gestion de l’énergie

A self-management strategy in which a person with ME/CFS organizes their activities to stay within their energy limits, with support from a professional; activity is never automatically increased ^[1].

7. Exercise intolerance — intolérance à l’effort

Symptoms or limitation during physical activity. Post-exertional malaise is different: it is often delayed, out of proportion and prolonged, and it can follow cognitive, emotional or social activity, not only physical activity ^[1].

8. Flare-up — poussée symptomatique

A worsening of symptoms beyond usual day-to-day variation, which is transient and generally resolves within a few days; it most often occurs as part of post-exertional malaise, but other symptoms, such as pain, can worsen without post-exertional malaise ^[1].

9. Relapse — rechute

A sustained and marked worsening of symptoms, longer than a flare-up, that requires a substantial and lasting adjustment to energy management ^[1].

10. Daily functioning — fonctionnement quotidien

The ability to carry out personal, occupational, educational and social activities. A reduction compared with the previous level is part of the criteria for ME/CFS ^{[2, 1]}.

Orthostatic function and the autonomic nervous system

11. Orthostatic intolerance (OI) — intolérance orthostatique

A set of symptoms rather than a single diagnosis: symptoms (lightheadedness, feeling faint or fainting, difficulty concentrating, headaches, visual disturbances, palpitations…) appear or worsen when standing upright and improve, though not necessarily resolve, when sitting or lying down ^{[1, 2, 18]}. The term covers several entities, including POTS and orthostatic hypotension. See Orthostatic intolerance.

12. Postural orthostatic tachycardia syndrome (POTS) — syndrome de tachycardie orthostatique posturale

A form of chronic orthostatic intolerance characterized by an excessive increase in heart rate on moving to an upright position, without orthostatic hypotension; the thresholds depend on age and on the reference document ^{[1, 18, 19]}. Its diagnosis relies on symptoms and specific hemodynamic criteria, measured during an active stand test or a tilt-table test ^[3]. See What is POTS?.

13. Dysautonomia — dysautonomie

An umbrella term, synonymous with autonomic dysfunction, that refers to a disturbance of the autonomic nervous system and covers several disorders, including POTS ^[4]. On its own, it specifies neither the diagnosis nor the cause. See The autonomic nervous system and dysautonomia.

Hypermobility

14. Hypermobile Ehlers-Danlos syndrome (hEDS) — SED hypermobile (SEDh)

A type of Ehlers-Danlos syndrome defined by the 2017 classification; it is diagnosed clinically (examination, personal history, exclusion of other disorders) and no genetic test can currently confirm it ^{[5, 3]}. It is distinct from simple hypermobility without symptoms. See Joint hypermobility, HSD and hypermobile EDS and The 2017 hEDS criteria.

15. Hypermobility spectrum disorder (HSD) — trouble du spectre de l’hypermobilité (DSH)

Symptomatic joint hypermobility, with musculoskeletal manifestations, in a person who does not meet the criteria for hEDS, in the absence of another identified condition, notably a systemic rheumatologic disease ^[5]. See Joint hypermobility, HSD and hypermobile EDS.

16. Generalized joint hypermobility (GJH) — hypermobilité articulaire généralisée

A range of joint motion greater than usual in several joints, which may cause no symptoms or may be part of a disorder. It is studied separately from hEDS/HSD: its reported coexistence with fibromyalgia varies widely across studies ^[6]. For children, see Hypermobility in children.

Pain and fibromyalgia

17. Fibromyalgia (FM) — fibromyalgie

A disease whose main symptom is diffuse, prolonged chronic pain (lasting more than three months), associated with other non-specific symptoms such as fatigue, sleep problems, and cognitive or digestive problems ^[7]. See Fibromyalgia and related conditions.

18. Nociplastic pain — douleur nociplastique

Pain arising from functional changes in the nociceptive system, without evidence of tissue damage activating nociceptors or of a lesion of the somatosensory system; several pain mechanisms can coexist in the same person ^[7].

19. Central sensitization — sensibilisation centrale

A physiological concept referring to increased responsiveness of pain circuits in the central nervous system. The French National Authority for Health (HAS) describes fibromyalgia as linked to changes in the detection and modulation of pain in the central nervous system, which show up as a generalized hypersensitivity to pain ^[7]. It is neither a stand-alone diagnosis nor a strict synonym for nociplastic pain.

20. Widespread pain — douleur diffuse

Pain affecting several regions of the body; its distribution is used in the 2016 ACR criteria for fibromyalgia, which require involvement of at least four of five regions ^{[8, 9]}.

21. Widespread Pain Index (WPI) — indice de douleur diffuse

A score in the ACR criteria that counts, over the previous week, the painful areas among 19 areas grouped into five regions ^{[9, 8]}.

22. Symptom Severity Scale (SSS) — échelle de sévérité des symptômes

A score in the ACR criteria (0 to 12) that assesses the severity of fatigue, waking unrefreshed and cognitive symptoms, as well as the presence of headaches, abdominal pain or cramps, and depression ^{[9, 8]}.

Digestive system

23. Disorder of gut–brain interaction (DGBI) — trouble de l’interaction intestin-cerveau

A group of disorders characterized by chronic or recurrent digestive symptoms in the absence of a structural disease that readily explains these symptoms ^[10]. See Digestive problems, DGBI and dysmotility.

24. Functional gastrointestinal disorder (FGID) — trouble fonctionnel gastro-intestinal

The former name for DGBI, still found in publications. It was abandoned because the word “functional” is non-specific and can be perceived as stigmatizing ^[10]; Rome V reduces use of this term ^[11].

25. Gastrointestinal dysmotility — dysmotilité digestive

An abnormality in the movement or coordination of the digestive tract. It cannot be inferred from a single symptom: in certain situations, the AGA suggests tests of gastric function or of defecation ^[3].

26. Gastroparesis — gastroparésie

A disorder of stomach emptying, identified by measuring gastric emptying after anatomical and structural causes have been excluded ^[3]. It should not be diagnosed on the basis of nausea or a feeling of fullness alone. See Digestive problems, DGBI and dysmotility.

27. Irritable bowel syndrome (IBS) — syndrome de l’intestin irritable

A DGBI defined in Rome V by recurrent abdominal pain or discomfort, on average at least three days per month over the last three months, associated with at least two criteria: related to defecation, a change in stool frequency, a change in stool form ^{[12, 11]}.

28. Visceral hypersensitivity — hypersensibilité viscérale

Amplified perception of signals coming from the internal organs; it is one of the mechanisms proposed to explain DGBI, not proof of a structural lesion ^[10].

29. Bloating — ballonnement

A sensation of abdominal swelling or pressure. The Rome V criteria distinguish it from visible abdominal distension ^[12].

Cognition

30. Brain fog — brouillard cérébral

An expression used to describe cognitive difficulties: finding words or numbers, slowed responsiveness, short-term memory, concentration, multitasking ^[1]. It is not a stand-alone medical diagnosis. See Brain fog.

31. Working memory — mémoire de travail

The ability to temporarily hold and manipulate information during a task. It is described as a foundational system on which more complex cognitive processes rely ^[13].

32. Processing speed — vitesse de traitement

How quickly a person perceives information, processes it and responds to it. It was reduced in women with POTS in the study by Arnold et al. ^[14].

33. Selective attention — attention sélective

The ability to focus attention on relevant information while filtering out distractions. It was the primary outcome of the study by Arnold et al. on POTS ^[14].

34. Executive function — fonctions exécutives

A set of cognitive control processes (mental flexibility, inhibition, planning, keeping track of a task). In the study by Arnold et al., lower scores suggested difficulties with tracking and mental flexibility ^[14].

35. Word-finding difficulty — difficulté à trouver ses mots

Difficulty retrieving the right word when speaking or writing; NICE lists difficulty finding words or numbers among the cognitive difficulties of ME/CFS ^[1].

36. Episodic memory — mémoire épisodique

Memory of lived events, recorded in a specific spatial and temporal context; it involves encoding, storage, retrieval and recognition of information ^[15].

37. Fibro-fog — « fibro-fog »

An informal expression for the loss of mental clarity reported in fibromyalgia ^[16]; French texts use the English term as is. It is not an independent diagnosis. See Brain fog.

Cross-cutting concepts

38. Long COVID / post-COVID condition — COVID long

Effects that may persist after acute COVID-19 has resolved; the CDC states that more than 200 symptoms have been identified ^[17]. Institutional definitions vary by country and authority. See POTS and long COVID.

39. Multidisciplinary care — prise en charge multidisciplinaire

Coordination of several disciplines according to a person’s needs and symptoms, when appropriate ^[3]; in France, HAS provides for possible referral for a multidisciplinary assessment at a chronic pain center for fibromyalgia ^[7]. This does not mean that every specialty must routinely be involved.

40. Proposed mechanism — hypothèse de mécanisme

A biological explanation put forward for a phenomenon, to be distinguished from a mechanism demonstrated by robust experimental data. For example, the AGA states that, for the links between hEDS/HSD, POTS and MCAS, theoretical explanations exist but experimental evidence is limited ^[3].

Written by

AI-assisted literature research (ChatGPT) and AI-assisted writing (Claude)

Editor

Jean Viry-Babel

Review status

Clinical review: Dr Françoise Charmoillaux (anesthesiologist)

Approved on

9 November 2026

Literature search

8 November 2026

Last verified

9 November 2026

Geographic scope

international, United States, France, United Kingdom

Audience

everyone

Conflicts of interest

No known financial ties. Separately, the publisher is developing a personal approach to these conditions under the name Connected Conditions, which is not cited here (see the legal notice).

Limitations of this page

Short educational definitions: they do not replace the full diagnostic criteria and cannot be used for self-diagnosis. General cognitive psychology definitions are given without a specific source; only sentences followed by a reference are sourced.