What does decimal mean?
Decimal is a term from mathematics referring to numbers expressed in the base-ten system — the system humans use universally because we count on ten fingers. As a noun, a decimal typically denotes a fractional value written with a decimal point, such as 0.75, which represents three-quarters. As an adjective, it describes anything organised around tens: decimal currency, decimal notation, the decimal system. Decimals allow precise representation of quantities that fall between whole numbers, making them indispensable in finance, science, engineering, and everyday measurement. The word derives from Latin decimus ('tenth'), itself from decem ('ten'), linking it to words like December (the tenth month of the old Roman calendar) and decimate. While fractions express parts of a whole as a ratio, decimals express them positionally after a point, which makes them easier to compare, order, and compute. Its connotations are neutral and technical — a workhorse of arithmetic rather than rhetoric.
A number expressed in the base-ten system, especially one written with a decimal point to represent a fraction.
"Write your answer as a decimal rather than a fraction."
Often used attributively in phrases like 'decimal point' or 'decimal places'.
Relating to or based on the number ten; reckoned or denominated in tens.
"Most of the world now uses decimal currency."
Frequently appears in fixed compounds such as 'decimal system' and 'decimal notation'.
Standard plural; used when discussing multiple base-ten fractional numbers.
"Recurring decimals repeat a pattern indefinitely after the decimal point."
The word 'decimal' hides 'decem', Latin for ten — every time you write 0.5, you're speaking ancient Rome's language of counting.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of decimal
Decimal comes from the Medieval Latin 'decimalis', meaning 'of tenths', derived from Latin 'decimus' ('tenth'), from 'decem' ('ten'). It entered English in the early 17th century, initially in mathematical and astronomical writing before spreading into commerce and measurement. It shares its root with other Latinate terms built on decem, including December, decimate, and the metric unit decimeter.
Related word forms
How decimal is actually used
Both noun and adjective senses are standard and neutral in register; the noun is most frequent in everyday mathematical contexts.
Easily confused with decimal
Despite a similar opening, 'decline' means to refuse or decrease, while 'decimal' refers to the base-ten numbering system.