NOTATION, a marking. In architec ture it is a system of signs, marks, or characters appended to figures, when used to denote dimensions on drawings, as ' for feet, " for inches, "' for parts; as 10' 6" = 10 feet, 6 inches. In arith metic it is a system of figures or char acters used to represent numbers. Two methods of so doing are at present in use, the Roman and the Arabic.
In the Roman method seven characters are employed called numeral letters. These standing separately represent the following numbers: I. for 1, V. for 5, X. for 10, L. for 50, C. for 100, D. for 500, M. for 1,000. When a letter stands alone, it represents the number given above, as V. for 5; when a letter is re peated the combination stands for the product of the number denoted by the letter by the number of times which it is taken: thus, III. stands for 3, XXX. for 30, etc.; when a letter precedes another, taken in the order given above, the combination stands for the num ber denoted by the greater diminished by that denoted by the less: thus, IV. stands for 5 less 1, i. e., 4; XC. for 100 less 10, i. e., 90, etc.; when a letter, taken in the order given above, follows another, the combination stands for the sum of the numbers denoted by the letters taken separately; thus, XI. stands for 10 plus 1, etc.
In the Arabic, or rather the Hindu, method, introduced by the Arabs into Eu rope at the close of the 10th century, numbers are represented by the symbols, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and their com binations according to conventional rules. The characters are called figures or digits and taken in their order, stand for naught, one, two, three, four, five, six, seven, eight, nine; the value of the unit depends on the place which the figure occupies in the scale adopted. The value of each figure or digit increases in a tenfold ratio from the right to the left.
Notation in chemistry is the written language of that science. The system now in use belongs exclusively to modern times, but in all ages signs of some kind or other seem to have been employed to represent the various kinds of matter. In 1815 Berzelius proposed using the initial letter of the element and of co efficients for the number of like atoms in a compound, as sulphate of soda=NA, SO4. In organic compounds, the con stitution of which is known, the symbols are so arranged as to show the various CH2 groups of radicals CO (C2H2) 0 =ethylic acetate, but butyric acid, with the same number of atoms, is expressed by CH9 (CHI) 1.