A decimal is a fraction written in a special form. Instead of writing 1/2, for example, you can express the fraction as the decimal 0.5, where the zero is in the ones place and the five is in the tenths place.

Decimal comes from the Latin word decimus, meaning tenth, from the root word decem, or 10. The decimal system, therefore, has 10 as its base and is sometimes called a base-10 system. Decimal can also specifically refer to a number in the decimal system. As an adjective, decimal means something related to this numbering system. The decimal point, for example, refers to the period that separates the ones place from the tenths place in decimal numbers.

Definitions of decimal
  1. noun
    a number in the decimal system
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    type of:
    a concept of quantity involving zero and units
  2. adjective
    numbered or proceeding by tens; based on ten
    “the decimal system”
    synonyms: denary
    expressible as a quantity or relating to or susceptible of measurement
  3. noun
    a proper fraction whose denominator is a power of 10
    synonyms: decimal fraction
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    circulating decimal, recurring decimal, repeating decimal
    a decimal with a sequence of digits that repeats itself indefinitely
    type of:
    proper fraction
    a fraction with a numerator smaller than the denominator
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