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.
A substitution is a mutation that exchanges one base for another (i.e., a change in a single chemical letter such as switching an A to a G). Such a substitution could: 1  change a codon to one that encodes a different amino acid and cause a small change in the protein produced.2  For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which alters a single amino acid in the protein produced. For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which alters a single amino acid in the protein produced. 2  change a codon to one that encodes the same amino acid and causes no change in the protein produced. 3  These are called silent mutations.