One important aspect of precision is choosing the right word. Another important aspect of being precise is choosing the appropriate level of accuracy. Just as you wouldn't assign the wrong number of significant digits to a numeral in a calculation, so shouldn't you assign an inappropriate level of accuracy to details in your writing. The appropriate level of detail depends upon your work and your audience. Many ordinary words have specific meanings as well.
Water is comprised of hydrogen and oxygen.
A precise way to write this sentence is Water is composed of hydrogen and oxygen. There are several word pairs that give difficulty not only to scientists and engineers, but to all writers. Listed below are some of these word pairs and the differences in their meanings. As is a conjunction and introduces a clause. As an adjective, principal means main or most important.