The number "309" can refer to various things depending on the context. Here are some prominent meanings:

• It is a bus route number in Berlin, Germany. The Berlin bus 309 runs from U Wilmersdorfer Str./S Charlottenburg to Schlosspark-Klinik, with 12 stops, operating daily with approximately 15 minutes trip duration.

• It is a year in history, specifically the year 309 AD in the Julian calendar, known as the Year of the Consulship of Licinianus and Constantius in the Roman Empire.

• It is a section number in German law, for example:
  • § 309 in the German Strafgesetzbuch (Criminal Code) addresses misuse of ionizing radiation, prescribing penalties from imprisonment to life sentences depending on the severity of harm caused.

* § 309 in the German Bürgerliches Gesetzbuch (Civil Code) lists clauses that are prohibited in general terms and conditions of contracts without room for valuation, covering contract law limitations.

• It is the name/number of a bus route in London, UK, where route 309 runs towards Bethnal Green.

• It is the subclass number for the Australian Partner (Provisional) visa, subclass 309, which allows partners of Australian citizens or residents to live temporarily in Australia.

If a more specific meaning or context for "309" is needed, please specify.