Why is one thousand called 1 K? (And not 1T)

Well, we all know and have seen 1K in the world of numbers and abbreviations, referring to one thousand. But why do we use 'K' and not 'T' for thousands? The reason lies in the history of languages and the metric system.

The Greek connection
The use of 'K' to indicate a thousand is borrowed from the Greek word 'chilioi' which means 'thousand.' This term was borrowed from the metric system that also uses prefixes to show multiples of ten. The prefix 'kilo-' has been derived from 'chilioi' and it indicates one thousand units. For example, a kilogram indicates one thousand grams, and a kilometer indicates one thousand meters.
Impact of the metric system
A French invention in the late 18th century assigned prefixes such as 'kilo-' to standardize its application in the metric system to make extensive number-writing easier. The metric system is assumed to be universal and simple, thus helpful in articulating scientific and mathematical concepts irrespective of language and region. Since the use of the metric system was widely adopted throughout the globe, the application of 'kilo-' and its unit symbol 'K' also gained massive usage.

Why not 'T'?
While 'K' is derived from the Greek 'chilioi',' 'T' has no original connection in the history or language with the sense of a thousand. The letter 'T' is used quite commonly, though, as an abbreviation for 'tera-', which is one trillion in scientific and technical terms (1,000,000,000,000). In scientific and technical writing where 'Kilo' is used to denote a thousand, for instance, Using 'T' for a thousand could lead to confusion, especially in scientific and technical contexts where precise terminology is crucial.
Practical usageIn everyday language, 'K' is used to replace high values when describing long numbers, such as monetary terms. Therefore, $10,000 is often written as $10K. This makes it easier to write and read big numbers without changing the understanding. The use of 'K' has become so common that it is even regarded as one of the ways of writing numbers in the present world and is seen most popularly on social media.


Cultural adoption
Not only English-speaking countries use 'K' to refer to thousands. Other languages and cultures worldwide also use shorthand because of the influence of the metric system and global communication in science and technology. Such wide dissemination makes all the more valid the use of 'K' as a universal symbol for one thousand.

'K' stands for thousands through historical, linguistic, and practical reasons. Coming from the Greek word chilioi and being popularized during the metric system, 'K' is a widely understood shorthand for a thousand. The lack of a similar historical or linguistic foundation of using 'T' for thousand, and because it would compete in confusion with 'tera-', 'K' prevails. Consequently, '1K' is extensively used in daily life and technical analyses. The use of 'K' for thousands is also handy in digital spaces like social media and coding, where space is limited. It makes communication faster and easier, especially in fields like finance and marketing.