Dorland's Illustrated Medical Dictionary / Oxford English Dictionary

• abscess — (Medicine) A localized collection of pus within a tissue or organ, formed as a result of an acute inflammatory process, usually caused by a local bacterial infection.
• Acephalocyst — A vesicular, sterile form of an echinococcus (Taenia echinococcus) that lacks a scolex (head), encountered in hydatid disease or hydatid cysts in humans and animals. It represents a parasitic vesicle that contains no brood capsules or fertile scoleces capable of reproduction, accumulating a clear liquid within host tissues, notably the liver or lungs.
• Acellular — Not composed of cells, lacking a cellular structure, or independent of typical cellular organization. In virology, the term describes biological entities like viruses or viroids that lack an independent metabolism and rely on a host cell; in histology and bioengineering, it refers to tissues or extracellular matrices from which all cellular components have been removed.
• Acetonemia — A pathological condition defined by the abnormal presence or accumulation of acetone and other ketone bodies in the blood. It occurs as a result of faulty carbohydrate metabolism, forcing the body to excessively burn fats for energy, commonly encountered in insulin-dependent diabetes mellitus, starvation, fever, or severe hepatic disorders.
• Aphasia — A severe communication disorder consisting of the total or partial loss of the ability to speak, write, and understand articulate or written language, occurring in the absence of sensory deficits or vocal apparatus impairment. It is triggered by acquired organic lesions in the cerebral cortex, primarily affecting the language-dominant hemisphere.
• Affection / Fondness — A noun with two primary meanings. Emotionally, it denotes a steady feeling of fondness, attachment, warmth, or love toward someone. Clinically, it refers to a pathological condition, disease, lesion, or functional disorder of an organ or biological system.
• Aphtha — A small, painful, superficial ulceration, whitish or yellowish in color, surrounded by an inflammatory reddish border, appearing on the oral mucosa. It can be solitary or multiple, triggered by immune factors, stress, local trauma, or vitamin deficiencies, featuring a benign and recurrent nature.