A509

A509 is a designation that can refer to several different things, most commonly a road or a type of paper. In the United Kingdom, A509 is a road that runs through Bedfordshire and Northamptonshire. It connects the A421 near Bedford to the A43 near Kettering, passing through towns such as Kimbolton and Thrapston. The road is primarily a single carriageway for much of its length.

In the context of paper, A509 is a specific size within the ISO 216 standard for paper dimensions. This standard defines a series of paper sizes based on the A series, where each subsequent size is half the area of the previous one. The A509 size is not a standard ISO A series paper size. Standard A series sizes include A0, A1, A2, A3, A4, A5, A6, and so on, with A4 being the most common for office use. There is no officially recognized paper size designated as A509 within this international standard. Therefore, when encountered, A509 is more likely to refer to the road in the UK.