From Longman Dictionary of Contemporary EnglishSilicon ValleyˌSilicon ˈValley a part of California, in the area between San Francisco and San José, which is known as a centre of the computer industry. Many important inventions were discovered in this area, and many large and small companies producing computer software and hardware are based there. It is called Silicon Valley because the computer industry is based on the silicon chip.From Longman Business DictionarySilicon ValleyˌSilicon ˈValley nounCOMPUTING the area of California between San Francisco and San Jose, which is known as a centre of the computer industry
