| lethal | Deadly, fatal. Origin: L. Lethalis, from lethum = death (18 Nov 1997) |
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| lethal coefficient | <microbiology> That concentration of disinfectant that kills bacteria at 20-25캜 in the shortest period of time. (05 Mar 2000) |
| lethal dwarfism | Dwarfism leading to intrauterine or neonatal death. (05 Mar 2000) |
| lethal equivalent | A combination of selective effects that on average have the same impact on the composition of the gene pool as one death; e.g., two carriers at 50% risk of dying would be the lethal equivalent of one carrier at 100% risk, in the population genetics of recessive traits lethal equivalent is expressed as twice the sum of the expected number of deaths ascribable to the genetic load. Expression used of the genetic load of recessive genes in heterozygous state that if in homozygous state would cause death or carry a risk of death. The expected number of deaths from all such genes is expressed in lethal equivalent. (05 Mar 2000) |
| lethal factor | A disorder that prevents effective reproduction by those affected; e.g., Klinefelter syndrome. (05 Mar 2000) |
| lethal gene | A gene that produces a genotype that leads to death of the organism before reproduction is possible or that precludes reproduction; for a recessive gene the homozygous or hemizygous state is lethal. (05 Mar 2000) |
| lethal midline granuloma | Destruction of the nasal septum, hard palate, lateral nasal walls, paranasal sinuses, skin of the face, orbit and nasopharynx by an inflammatory infiltrate with atypical lymphocytic and histiocytic cells; presumably a form of lymphoma in most cases. An obsolete term for polymorphic reticulosis. Synonym: granuloma gangrenescens, malignant granuloma, midline malignant reticulosis granuloma. (05 Mar 2000) |
| lethal mutation | <genetics, molecular biology> Mutation that eventually results in the death of an organism carrying the mutation. (18 Nov 1997) |
| biological half-life | <biochemistry, biology> This is the time required for one-half of the total amount of a particular substance in a biological system to be consumed or broken down by biological processes when the rate of removal is approximately exponential. Toxic chemicals with a long biological half-life (such as some pesticides) will tend to accumulate in the body and are, therefore, more likely to be harmful. A substance with a short biological half-life may still accumulate if a portion of it it becomes tightly bound to bone or other tissues, even if most of it is quickly cleared from the body. (21 Mar 1998) |
| red half-moon | <clinical sign> Irregular red discoloration of the usually pale demilune at the base of the fingernail; may be seen in congestive failure, malignant disease, or liver disease, but not specific for any of these. (05 Mar 2000) |
| physical half-life | The time required for half the atoms of a radionuclide to undergo disintegration. (05 Mar 2000) |
| half | In an equal part or degree; in some pa appromating a half; partially; imperfectly; as, half-coloured, half done, half-hearted, half persuaded, half conscious. "Half loth and half consenting." "Their children spoke halfin the speech of Ashdod." (Neh. Xiii. 24) 1. Consisting of a moiety, or half; as, a half bushel; a half hour; a half dollar; a half view. The adjective and noun are often united to form a compound. 2. Consisting of some indefinite portion resembling a half; approximately a half, whether more or less; partial; imperfect; as, a half dream; half knowledge. "Assumed from thence a half consent." (Tennyson) Half ape, a middle or intermediate tint, as in drawing or painting. See Demitint. Half truth, a statement only partially true, or which gives only a part of the truth. Half year, the space of six moths; one term of a school when there are two terms in a year. Origin: AS. Healf, half, half; as a noun, half, side, part; akin to OS, OFries, & D. Half, G. Halb, Sw. Half, Dan. Halv, Icel. Halfr, Goth. Halbs. Cf. Halve, Behalf. Source: Websters Dictionary (01 Mar 1998) |
| half-a-gram stain | <technique> A lab technique used to detect the presence of members from the bacterial family Legionellaceae in samples of sputum. (09 Oct 1997) |
| half amplitude pulse duration | The time, in milliseconds, required for a wave form to reach half of its full magnitude. (05 Mar 2000) |
| half-axial projection | Reverse tilted AP radiographic projection devised to permit demonstration of the entire occipital bone, foramen magnum, and dorsum sellae, as well as the petrous ridges. Synonym: half axial view, half-axial projection, Towne view. (05 Mar 2000) |