Introduction

Have you noticed that minute is shorten sometimes as min and sometimes as mn? Likewise for hour with h and hr, for second with s and sec, for gram with g and gr, and for many other units.

Have you also noticed that sometimes a space is present between a value and a unit symbol (e.g. 10 s), and sometimes not (e.g. 10s)?

Of course, only one way is correct, and in theses examples, the first possibility is the correct one. Check the cheat sheet to see at a glance the main rules about writing correctly mathematical symbols, units symbols, and quantities.

Cheat Sheet

References

1. BIPM, The International System of Units (SI), 2019 (updated in 2022), https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf
2. NIST, Guide for the use of the International System of Units (SI), NIST Special Publication 811, 2008, https://physics.nist.gov/cuu/pdf/sp811.pdf
3. ISO, ISO 80000-2:2019, Quantities and units — Part 2: Mathematics, 2019 (updated in 2021), https://www.iso.org/standard/64973.html
4. IEC, IEC 80000-13:2008, Quantities and units — Part 13: Information science and technology, 2008, https://www.iso.org/standard/31898.html
5. IEEE, IEEE 260.1-2024, IEEE Approved Draft Standard Letter Symbols for Units of Measurements, 2024, https://standards.ieee.org/ieee/260.1/6864
6. IEEE, IEEE 1541-2021, IEEE Standard for Prefixes for Binary Multiples, 2021, https://standards.ieee.org/ieee/1541/6867