substitution

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The act or an instance of substituting.
2. n. The state of being substituted.
3. n. One that is substituted; a replacement.

Century Dictionary and Cyclopedia

1. n. The act of substituting, or putting (one person or thing) in the place of another; also, the state or fact of being substituted.
2. n. The office of a substitute: delegated authority.
3. n. In grammar, the use of one word for another; syllepsis.
4. n. In Roman law, the effect of appointing a person to be heir, in case the heir first nominated would not or could not be heir. This was called vulgar substitution. Pupilary substitution existed where, after instituting his child as heir, the testator directed that, if after the child should have become heir it should die before attaining puberty, another be substituted in its place. This was originally allowed only for children under age in the power of the testator, but was afterward extended to children who for any reason could not make a valid will.
5. n. In French law, a disposition of property whereby the person receiving it, who is called the institute (le grévé), is charged either at his death or at some other time to deliver it over to another person called the substitute (l'appelé).
6. n. In chem., the replacing of one or more elements or radicals in a compound by other elements or radicals. Thus, by bringing water and potassium together, potassium (K) is substituted for a hydrogen atom in water (H₂O), yielding KOH, or caustic potash. By further action the other hydrogen atom may be replaced, yielding potassium oxid (K₂O). Substitution is the principal method employed in examining the chemical structure of organic bodie's. Also called metalepsy.
7. n. In algebra: The act of replacing a quantity by another equal to it; also, in the language of some algebraists, the replacement of a set of variables by another set connected with the first by a system of equations equal in number to the number of variables in each set. See transformation (which is the better term).
8. n. The operation of changing the order of a finite number of objects, generally letters, that are in a row, the change following a rule according to which the object in each place is earned to some definite place in the row, this operation being regarded as itself a subject of algebraical operations. For example, supposing we were to start with the row a, b, c, d, e, a substitution might consist in carrying us to the row b, c, a, e, d. Denoting this substitution by S, the repetition of it, which would be denoted by S, would carry us to c, a, b, d, e. If T denote the substitution of e, d, c, b, a for a, b, c, d, e, then TS would convert the last row into d, e, a, c, b, while ST would convert it into d, c, e, a, b. One way of denoting a substitution to which the terminology of the theory refers is to write a row upon which the substitution could operate, with the resulting row above it. These two rows are called the terms of the substitution, the upper one the numerator, the lower the denominator of the substitution. The objects constituting the rows are called the letters of the substitution.
9. n. A linear transformation.
10. n. In biology: The assumption by one organ of a function which was at one time performed by another organ. Thus the swim-bladder in fishes shows “that an organ originally constructed for one purpose, namely, notation, may be converted into one for a wholly different purpose, namely respiration.”
11. n. The acquisition by an organ of a secondary function which, at first performed incidentally, may gradually become the chief function if the primary function becomes useless or is performed by another organ. Thus “the little folds of skin which originally served as ovigerous frena, but which, like-wise, very slightly aided the act of respiration, have been gradually converted by natural selection into branchiæ, simply through an increase in their size and the obliteration of their adhesive glands.”
12. n. In Scots law, a technical enumeration of a series of heirs.
13. n. In civil law, the appointment, in a will, of a successor to a devisee or legatee; subrogation.

Wiktionary

1. n. the act of substituting or the state of being substituted
2. n. a substitute or replacement
3. n. chemistry (especially in organic chemistry) the replacement of an atom, or group of atoms, in a compound, with another

GNU Webster's 1913

1. n. The act of substituting or putting one person or thing in the place of another
2. n. The state of being substituted for another.
3. n. rare The office or authority of one acting for another; delegated authority.
4. n. (Civil Law) The designation of a person in a will to take a devise or legacy, either on failure of a former devisee or legatee by incapacity or unwillingness to accept, or after him.
5. n. (Theol.) The doctrine that Christ suffered vicariously, being substituted for the sinner, and that his sufferings were expiatory.
6. n. (Chem.) The act or process of substituting an atom or radical for another atom or radical; metathesis; also, the state of being so substituted. See Metathesis.

WordNet 3.0

1. n. the act of putting one thing or person in the place of another:
2. n. an event in which one thing is substituted for another