By Kimberly Amadeo. Definition: Silicon Valley is the center for innovative technology companies. It's located in the are around San Francisco, California.It's home to 2,000 tech companies, the densest concentration in the world. This proximity to suppliers, customers, and cutting edge research gives each a competitive advantage.ilicon Valley Companies. The most well-known Silicon Valley companies include Adobe, Apple, Cisco, eBay, Facebook, Google, Hewlett-Packard, Intel, Intuit, Netflix, Oracle, Salesforce.com, Tesla, Twitter, Yahoo! and Zynga.
Math definition of Substitution: Substitution - A strategy for solving systems of equations that include solving for one variable and using that solution to find the other variable. 1  Subject : Math.  Topic : Algebra 2.
Medical Definition of SUBSTITUTION. 1. : a chemical reaction in which one or more atoms or groups in a molecule are replaced by equivalent atoms or groups to form at least two products; especially: the replacement of hydrogen in an organic compound by another element or group. 2. Substitution of applesauce for oil is one way of reducing the fat in recipes. 2  The cookbook has a long list of substitutions for ingredients that may be hard to find.