We call these letters symbols. And an element is a pure substance made from only one type of atom. And there are quite a lot of elements. There are something like 100, and each has a unique symbol ...

If you are a first- or second-year student interested in the biochemistry major, you should take science courses that fulfill some of the major requirements and prepare you for the advanced courses ...

Symbols are included to depict mathematical functions, graphs, process equipment, instruments, and electrical equipment. The symbols are suitable for use in dynamic displays, as on cathode-ray tubes ...