A chain is a unit of length used in some older systems of measurement, particularly in surveying and land measurement. In the United States, one chain is equal to 66 feet or 22 yards. Internationally, it's defined as exactly 20.1168 meters.
Chains were historically used for measuring large plots of land and for surveying purposes, often in agriculture and real estate. However, the use of the chain as a standard unit of measurement has largely been replaced by the more modern and standardized metric and imperial systems, which use units like meters, feet, and yards.
The term "chain" comes from the practice of physically measuring land using a chain made of linked metal bars or wire. Each chain was typically 66 feet long, and surveyors would lay out chains end to end to measure distances across large areas. Today, modern surveying equipment such as electronic distance measuring devices (EDMs) and GPS technology have largely replaced the use of physical chains in land surveying.
A "twip" is a unit of measurement used in desktop publishing and computer graphics, especially in the context of Microsoft Windows. The term "twip" is an abbreviation for "twentieth of a point," and it is used to define very small distances and sizes.
In the twip system:
1 twip is equal to 1/20th of a point. 1 point (abbreviated as "pt") is equal to approximately 20 twips.
Because a point is roughly 1/72nd of an inch, 1 twip is approximately 1/1440th of an inch (or about 1/567 millimeters).
Twips are used in various applications, including word processing, graphics design, and layout software. They are particularly valuable for precise positioning and sizing of elements on a computer screen or when preparing documents for printing. The twip system is commonly used in Microsoft Windows-based applications and the Windows Graphics Device Interface (GDI).
For example, in Microsoft Word, you can set paragraph spacing or element positioning in twips to achieve fine control over the layout of your documents.