dec·i·mal 
(dĕsə-məl)
(dĕsə-məl)n.
1.
a. A linear array of digits that contains a single period, called the decimal point, is possibly preceded by a minus sign (-), and represents a real number, with each successive digit to the right of the decimal point indicating a multiple of the next negative power of 10, and each successive digit to the left of the decimal point indicating a multiple of the next non-negative power of ten, beginning with 100 = 1. For example, 245.3 represents the real number (2 × 102) + (4 × 101) + (5 × 100) + (3 × 10-1) = 200 + 40 + 5 + 3/10 , and -1.04 represents the real number (-1 × 100) + (-4 × 10-2). Also called mixed decimal.
b. Such an array of digits in which there are no nonzero digits to the left of the decimal point, representing a real number between -1 and 1. Also called decimal fraction.
2. A number written using the base 10.
adj.
1. Expressed or expressible as a decimal.
2.
a. Based on 10.
b. Numbered or ordered by groups of 10.
[Medieval Latin decimālis, of tenths or tithes, from Latin decima, a tenth part or tithe, from decem, ten; see dek in the Appendix of Indo-European roots.]
deci·mal·ly adv.