| phenotypic threshold | A quantitative genetic trait with a continuous distribution termed its liability may generate two kinds of phenotype, according to whether the liability lies above or below some critical threshold at about which a radical change in behaviour occurs. For instance, blood uric acid level is a liability with an approximately gaussian distribution. At a critical point of chemical saturation (the threshold crystallization occurs and the resulting gout or nongout is a threshold trait. (05 Mar 2000) |
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| minimum light threshold | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |
| convulsant threshold | The smallest amount of stimulation, electric current, or drug required to induce a convulsion. (05 Mar 2000) |
| speech reception threshold test | A test to determine the lowest sound intensity level at which fifty percent or more of the spondaic test words (words of two syllables having equal stress) are repeated correctly. (12 Dec 1998) |
| stimulus threshold | The lowest limit of any perception whatever. Compare: differential threshold. Synonym: stimulus threshold. (05 Mar 2000) |
| no-threshold concept | That the biologic effect of radiation is proportional to dose, even for minutely small doses. (05 Mar 2000) |
| swallowing threshold | The moment that the act of swallowing begins after the mastication of food, the critical moment of reflex action initiated by minimum stimulation, prior to the act of deglutition. (05 Mar 2000) |
| differential threshold | The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold. (12 Dec 1998) |
| displacement threshold | The least distinguishable break in the contour of a line. (05 Mar 2000) |
| dominance threshold number | The number at which 50 percent of the total dominance measure for a given stratum is represented by one or more plant species when ranked in descending order of abundance (i.e., from most to least abundant), when this number is immediately exceeded, the dominant species for the stratum are realised. (09 Oct 1997) |
| double-point threshold | The least degree of separation of two points applied to the body surface that permits of their being felt as two. (05 Mar 2000) |
| taste threshold | The minimum concentration at which taste sensitivity to a particular substance or food can be perceived. (12 Dec 1998) |
| threshold | 1. The point at which a stimulus first produces a sensation. 2. The lower limit of perception of a stimulus. 3. The minimal stimulus that produces excitation of any structure; e.g., the minimal stimulus eliciting a motor response. Synonym: limen. Origin: A.S. Therxold (05 Mar 2000) |
| threshold body | Any material (e.g., glucose) that is excreted in the urine only when its plasma concentration exceeds a certain value, termed its threshold. Synonym: threshold body. (05 Mar 2000) |
| threshold differential | The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold. (12 Dec 1998) |