Often in genealogy a researcher encounters an archaic medical term used for the cause of death, or perhaps in a journal or family correspondence, this list is intended to aid with interpreting those terms.

Sanguineous crust - Scab.
Scarlatina - Scarlet fever. A contagious febrile disease, caused by infection with the bacteria group. A beta-hemolytic streptococci (which elaborate a toxin with an affinity for red blood cells) and characterized by a scarlet eruption, tonsillitis, and pharyngitis.
Scarlet fever - A disease characterized by red rash. see Scarlatina.
Scarlet rash - Roseola.
Sciatica - Rheumatism in the hips.
Scirrhus - Cancerous tumors.
Scotomy - Dizziness, nausea and dimness of sight.
Scrivener's palsy - Writer's cramp.
Screws - Rheumatism.
Scrofula - Primary tuberculosis of the lymphatic glands, especially those in the neck. A disease of children and young adults, it represents a direct extension of tuberculosis into the skin from underlying lymph nodes. It evolves into cold abscesses, multiple skin ulcers, and draining sinus tracts. Synonym: king's evil.
Scrumpox - Skin disease, impetigo.
Scurvy - Lack of vitamin C. Symptoms of weakness, spongy gums and hemorrhages under skin.
Septic - Infected, a condition of local or generalized invasion of the body by disease-causing microorganisms (germs) or their toxins.
Septicemia - Blood poisoning.
Shakes - Delirium tremens.
Shaking - Chills, ague.
Shingles - Viral disease characterized by skin blisters (closely related to chickenpox - cannot get shingles unless previously affected by chickenpox. often brought on by stress. most commonly the blisteres develope on the back - extremely itching),
Ship fever - see Typhus.
Siriasis - Inflammation of the brain due to sun exposure.
Sloes - Milk sickness.
Small pox - Contagious disease characterized by fever and blisters.
Softening of brain - Result of stroke or hemorrhage in the brain, with an end result of the tissue softening in that area; apoplexy.
Sore throat distemper - Diphtheria or quinsy.
Spanish influenza - An epidemic influenza.
Spasms - Sudden involuntary contraction of muscle or group of muscles, like a convulsion.
Spina bifida - Deformity of spine.
Spotted fever - Either typhus or meningitis; cerebrospinal meningitis fever. see Typhus.
Sprue - Tropical disease characterized by intestinal disorders and sore throat.
St. Anthony's fire - Also erysipelas, but named so because of affected skin areas are bright red in appearance.
St. Vitus' dance - Ceaseless occurrence of rapid complex jerking movements performed involuntarily. see chorea.
Stomatitis - Inflammation of the mouth.
Stranger's fever - Yellow fever.
Strangery - Rupture.
Sudor anglicus - Sweating sickness.
Suffocation - The stoppage of respiration. In the nineteenth century, suffocation was reported as being accidental or homicidal. The accidents could be by the impaction of pieces of food or other obstacles in the pharynx or by the entry of foreign bodies into the larynx (as a seed, coin, or food). Suffocation of newborn children by smothering under bedclothes may have happened from carelessness as well as from intent. However, the deaths also could have been due to SIDS (sudden infant death syndrome), wherein the sudden and unexpected death of an apparently healthy infant, while asleep, typically occurs between the ages of three weeks and five months and is not explained by careful postmortem studies. Synonyms of SIDS: crib death and cot death. It was felt that victims of homicidal suffocation were chiefly infants or feeble and infirm persons.
Summer complaint - Diarrhea, usually in infants caused by spoiled milk. see Cholera infantum.
Sunstroke - Uncontrolled elevation of body temperature due to environment heat. Lack of sodium in the body is a predisposing cause.
Suppuration - The production of pus.
Swamp sickness - Could be malaria, typhoid or encephalitis.
Sweating sickness - Infectious and fatal disease common to UK in 15th century.

Tabes mesenterica - Tuberculosis of the mesenteric glands in children, resulting in digestive derangement and wasting of the body.
Teething - The entire process which results in the eruption of the teeth. Nineteenth-century medical reports stated that infants were more prone to disease at the time of teething. Symptoms were restlessness, fretfulness, convulsions, diarrhea, and painful and swollen gums. The latter could be relieved by lancing over the protruding tooth. Often teething was reported as a cause of death in infants. Perhaps they became susceptible to infections, especially if lancing was performed without antisepsis. Another explanation of teething as a cause of death is that infants were often weaned at the time of teething; perhaps they then died from drinking contaminated milk, leading to an infection, or from malnutrition if watered-down milk was given.
Tetanus - An infectious, often-fatal disease caused by a specific bacterium, Clostridium tetani, that enters the body through wounds; characterized by respiratory paralysis, high fever, and tonic spasms and rigidity of the voluntary muscles, especially those of the neck and lower jaw. Synonyms: trismus, lockjaw.
Thrombosis - Blood clot inside blood vessel.
Thrush - A disease characterized by whitish spots and ulcers on the membranes of the mouth, tongue, and fauces caused by a parasitic fungus, Candida albicans. Thrush usually affects sick, weak infants and elderly individuals in poor health. Now it is a common complication from excessive use of broad-spectrum antibiotics or cortisone treatment. Synonyms: aphthae, sore mouth, aphthous stomatitis.
Thyrotoxicosis - A disease affecting the thyroid gland.
Tick fever - Rocky mountain spotted fever.
Toxemia (of pregnancy) - see Eclampsia.
Trench mouth - Painful ulcers found along gum line, caused by poor nutrition and poor hygiene.
Trismus nascentium/neonatorum - A form of tetanus seen only in infants, almost invariably in the first five days of life, probably due to infection of the umbilical stump.
Tussis convulsiva - Whooping cough.
Typhoid fever - An infectious, often-fatal, febrile disease, usually occurring in the summer months, characterized by intestinal inflammation and ulceration caused by the bacterium Salmonella typhi, which is usually introduced by food or drink. Symptoms include prolonged hectic fever, malaise, transient characteristic skin rash (rose spots), abdominal pain, enlarged spleen, slowness of heart rate, delirium, and low white-blood cell count. The name came from the disease's similarity to typhus (see below). Synonym: enteric fever.
Typhus - An acute, infectious disease caused by several micro-organism species of Rickettsia (transmitted by lice and fleas) and characterized by acute prostration, high fever, depression, delirium, headache, and a peculiar eruption of reddish spots on the body. The epidemic or classic form is louse borne; the endemic or murine is flea borne. Synonyms: typhus fever, malignant fever (in the 1850s), jail fever, hospital fever, ship fever, putrid fever, brain fever, bilious fever, spotted fever, petechial fever, camp fever.

Undulant Fever - Intermittant fever caused by brucellosis. also called abortus fever.

Variola - Smallpox.
Venesection - Bleeding.
Viper's dance - St. Vitus' Dance.
Virus - An ultramicroscopic, metabolically inert infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals. In the early 1800s virus meant poison, venom, or contagion.

Water on brain - Enlarged head.
White swelling - Tuberculosis of the bone.
Winter fever - Pneumonia.
Womb fever - Infection of the uterus.
Worm fit - Convulsions associated with teething, worms, elevated temperature or diarrhea.

Yellow fever - An acute, often-fatal, infectious febrile disease of warm climates, caused by a virus transmitted by mosquitoes, especially Aledes aegypti, and characterized by liver damage and jaundice, fever, and protein in the urine. In 1900 Walter Reed and others in Panama found that mosquitoes transmit the disease. Clinicians in the late nineteenth century recognized "specific yellow fever" as being different from "malarious yellow fever." The latter supposedly was a form of malaria with liver involvement but without urine involvement. See epidemics for major outbreaks.
Yellowjacket - Yellow fever.