A taxi(public hire) is a public transport vehicle with less than 8 passenger seats, which is licensed to "ply for hire". This means that it may stand at ranks or be hailed in the street by members of the public. Private hire vehicles too must have less than 8 passenger seats but they need to be booked in advance by customers through an operator and may not ply for hire in the street. (For vehicles with more than 8 passenger seats the Public Service Vehicle Regulations apply).

This information is taken from the Department of Transport website(21/08/2006)

http://www.dft.gov.uk/