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(sig′năl) [L. signale, indication, visible sign] Any form of communication that provides information. It is usually oral, written, visual, or electronic, i.e., transmitted by radio, telephone, television, laser, or optical fibers.

cellular s. A chemical released by cells and tissues to stimulate metabolic activities within those tissues or in other parts of the body. Neurotransmitters, hormones, peptides, cytokines, arachidonic acid derivatives, and other chemicals are all signaling molecules.

electromyographic s. The electrical energy generated during muscular contraction.

signal-to-cut-off ratio

ABBR: S/co. A laboratory comparison of some measurable feature of a specimen to the standard set by the laboratory's positive control For example, in tests for antibodies to hepatitis C antibody, hepatitis C infection is not diagnosed unless a specific S/co is exceeded. Results that fall below the S/co can be found in noninfected patients and are considered to be false positive.


(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.


(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


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