1. Mathematical symbol: In mathematical formulas, variables and constants are usually expressed in italics. Such as x, y, z and other variables, π, e and other constants.

2. Physical quantities and units: Physical quantities and units are usually expressed in italics, such as speed v, current i, length l and time t, and units are meters (m), seconds (s) and kilograms (kg).

3. Loanwords: Words or phrases in loanwords are usually expressed in italics for easy distinction and emphasis. For example, people, as opposed to themselves, and so on.

4. Citation: When quoting other documents, information such as document name, periodical name and title should be expressed in italics to distinguish and attract attention.

5. Biological names: Genus names and species names in biological names are usually expressed in italics, which is easy to distinguish and emphasize. Such as Escherichia coli and Homo sapiens.

6. Variables and parameters: In the field of engineering technology, in order to facilitate the distinction and emphasis, variables and parameters are usually expressed in italics. Such as voltage v, resistance r, frequency f and other variables, as well as proportional coefficient k, damping coefficient zeta and other parameters.

7. Names and place names: In some cases, names and place names can also be expressed in italics for easy distinction and emphasis. Such as Einstein, Newton and other names, as well as Paris, London and other places.

It should be noted that when italics are used, corresponding specifications and requirements should be followed and consistency should be maintained. At the same time, when writing a paper, we should pay attention to clear thinking and strict logic, which is convenient for readers to understand and read.