International System of Units (SI Units) or MKS units for seven base quantities of measurements and their derived quantities are unified. Specific symbols are designated for all. Only symbols can be used or written in full spells for these units of measurement, for example, there are 30 s or 30 seconds in half a minute. Not 30 sec.
Note 1: Units are always written and read as singular. We can not write 30 seconds, yes it is 30 seconds.
Note 2: Always give one space after numbers and symbols. Example 35 s is correct. 35s is not correct.
Let us quickly see how to present the symbols of various units:
1. Time: symbol (s). Read as a second. It is small s . Writing 10 s and 10 Second is correct. Use of 10 Sec. or 10 SEC. Or 10 seconds is not correct.