n. [ Gr. me`las, -anos, black. ] [ 1913 Webster ]

1. An undue development of dark-colored pigment in the skin or its appendages; -- the opposite of albinism. [ 1913 Webster ]

2. (Med.) A disease; black jaundice. See Melaena. [ 1913 Webster ]

n. (Ethnol.) The character of having a high degree of pigmentation, as shown in dark skin, eyes, and hair. [ Webster 1913 Suppl. ]

n. [ Cf. F. mécanisme, L. mechanisma. See Mechanic. ] 1. The arrangement or relation of the parts of a machine; the parts of a machine, taken collectively; the arrangement or relation of the parts of anything as adapted to produce an effect; as, the mechanism of a watch; the mechanism of a sewing machine; the mechanism of a seed pod. [ 1913 Webster ]

2. The series of causal relations that operate to produce an effect in any system; as, the mechanism of a chemical reaction. [ PJC ]

3. Mechanical operation or action. [ 1913 Webster ]

He acknowledges nothing besides matter and motion; so that all must be performed either by mechanism or accident. Bentley. [ 1913 Webster ]

4. (Kinematics) An ideal machine; a combination of movable bodies constituting a machine, but considered only with regard to relative movements. [ 1913 Webster ]

n. (Medicine, Biochemistry) The mechanism{ 2 } by which a pharmacologically active substance produces an effect on a living organism or in a biochemical system; as, the mechanism of action of actinomycin involves its binding to DNA. The mechanism of action is usually considered to include an identification of the specific molecular targets to which a pharmacologically active substance binds or whose biochemical action it influences; a general recognition of the broad biochemical pathways (such as DNA synthesis, protein synthesis, cholesterol synthesis) which are inhibited or affected by a substance is termed its mode of action. [ PJC ]

n. [ Cf. F. mécanisme, L. mechanisma. See Mechanic. ] 1. The arrangement or relation of the parts of a machine; the parts of a machine, taken collectively; the arrangement or relation of the parts of anything as adapted to produce an effect; as, the mechanism of a watch; the mechanism of a sewing machine; the mechanism of a seed pod. [ 1913 Webster ]

2. The series of causal relations that operate to produce an effect in any system; as, the mechanism of a chemical reaction. [ PJC ]

3. Mechanical operation or action. [ 1913 Webster ]

He acknowledges nothing besides matter and motion; so that all must be performed either by mechanism or accident. Bentley. [ 1913 Webster ]

4. (Kinematics) An ideal machine; a combination of movable bodies constituting a machine, but considered only with regard to relative movements. [ 1913 Webster ]

n. (Medicine, Biochemistry) The mechanism{ 2 } by which a pharmacologically active substance produces an effect on a living organism or in a biochemical system; as, the mechanism of action of actinomycin involves its binding to DNA. The mechanism of action is usually considered to include an identification of the specific molecular targets to which a pharmacologically active substance binds or whose biochemical action it influences; a general recognition of the broad biochemical pathways (such as DNA synthesis, protein synthesis, cholesterol synthesis) which are inhibited or affected by a substance is termed its mode of action. [ PJC ]