High-definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SÉCAM, PAL) allow. Except for early analog formats in Europe and Japan, HDTV is broadcasted digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV).
Historically, the term high-definition television was also used to refer to television standards developed in the 1930s to replace the early experimental systems, although, not so long afterwards, Philo T. Farnsworth, John Logie Baird and Vladimir Zworykin had each developed competing TV systems but resolution was not the issue that separated their substantially different technologies. It was patent interference lawsuits and deployment issues given the tumultuous financial climate of the late '20s and '30s. Most patents were expiring by the end of World War II leaving the market wide open and no worldwide standard for television agreed upon. The world used analog PAL, NTSC, SÉCAM and other standards for over half a century.