Use symbols consistently and in keeping with the common practice of your discipline.
Biology, chemistry, engineering, mathematics, and physics, among many other fields, have extensive and precise systems to represent quantities, objects, and actions. Check with a relevant style guide, textbook, or handbook.
If you are not certain that your readers will recognize a symbol, give the full spelling in parentheses the first time you use the symbol. If your document contains a large number of symbols that may be unfamiliar to your readers, consider including a list of symbols in the front matter, following the list of tables.