A lakh (also written lac) is a unit in the Indian numbering system, widely used both in official and other contexts in Bangladesh, India, Nepal, Sri Lanka, Myanmar and Pakistan. One lakh is equal to a hundred thousand, i.e. (10 5 ). The word's use in the English language is particularly notable: In articles written for Indian audiences where the author is referring to the number 10 5 , the otherwise common expression "(a) hundred thousand" is almost never used; almost always the word lakh is used instead.

This system of measurement also introduces separators into numbers in a place that is different from that which is common in certain other number systems. For example, 30 lakh which is to say 3 million, would be written as 30,00,000 instead of 3,000,000. In this system of counting, a hundred lakhs make a crore, which is ten million.

In India, one lakh is written as 1,00,000. In most other parts of the world, the comma appears every three positions, so a lakh would usually be written as 100,000 outside India.

In India, the first comma appears after three places, but after every two places thereafter.

Examples of the Indian comma system: 12,12,12,123 5,05,000 7,00,00,00,000.

The same examples in the non-Indian system: 121,212,123 505,000 7,000,000,000