Semantics is the study of meaning. Meaning itself is a broad area of study. It can refer to lexical meaning or structural meaning (the meaning related to the structure of sentence). I will try to give the example of structural meaning. A sentence consists of pragmatic information and semantic information.
The polymerase chain reaction (PCR) is a technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence.n the second step, the temperature is lowered and the two DNA strands become templates for DNA polymerase to selectively amplify the target DNA. The selectivity of PCR results from the use of primers that are complementary to the DNA region targeted for amplification under specific thermal cycling conditions.
SCR means Silicon Controlled Rectifier. This device belongs to the family THYRISTORS. Thyristors denotes a family of semiconductor devices used for power control in DC and AC system. At present , the use of SCR is well spread and so vast that the word thyristor becomes synonymous with SCR. In construction, it is a pnpn device .