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(sĭg′nă-tūr) [L. signatura, to mark] 1. The part of a prescription giving instructions to the patient. 2. The act of writing one’s name on a document to certify its validity; the written name on the document.

signature molecule Biomarker.


(sī′nĕr) A person who communicates using sign language.


(sĭg-nĭf′ĭ-kănt) Important or meaningful.

significant break in coverage

Under U.S. law, 63 consecutive days without creditable health insurance coverage. In some states, the period is longer if the plan coverage is provided through an insurance policy or HMO.

significant other

A person with whom a patient has a close relationship, which may or may not include relatives or a spouse.


The use of sign language to communicate.

sign language

Representation of words by signs made with the position and movement of the fingers and hand. SEE: American Sign Language.


(sīn′owt″) Handoff.

signs of life

Spontaneous movements made by a comatose patient, esp. movements of the muscles of respiration.


(sĭl-dĕn′ă-fĭl) A phosphodiesterase type 5 inhibitor and anti-impotence agent, administered orally to treat erectile dysfunction.


(sī′lĕn-sĕr) A sequence of base pairs in DNA that prevents the transcription of a gene.


1. Making no sound or noise. 2. Of a gland, not secreting; nonsecretory. 3. In diagnosis, not clinically manifest, as in hypertension; asymptomatic. 4. In neurology, pert. to an association area that does not yield a detectable response when stimulated.

silent area

Any cortical area in the brain that on stimulation produces no detectable motor activity or sensory phenomenon, and in which a lesion may occur without producing detectable motor or sensory abnormalities.

silent disease

A disease that produces no clinically obvious symptoms or signs. Examples include hypertension, many forms of cancer (including small lesions of the breast and prostate cancer), and hearing loss, which may be either not noticed or denied by the individual. Many diseases begin silently, becoming obvious only when they are advanced.

silent rupture

SEE: under rupture.


(sil′ĭ-kă) [L. silex, flint] SiO2; silicon dioxide. SEE: silicon.

siliceous, silicious

(sĭ-lish′ŭs), adj.


(sĭl′ĭ-kāt) [L. silicus, flintlike] A salt of silicic acid.

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