Use the full word. Preferable to "about".
Don't abbreviate to "approx.", or worse, the symbol "~".
The luminosity of the LHC has increased by approximately 16% over the last two months.
A unit of area. A barn is 10−28 m2 (100 fm2), about the cross-sectional area of a uranium nucleus.
A barn expresses the cross section of any scattering process, which relates to the probability of interaction between small particles.
The prefix bio takes no hyphen. So,
Use minimal capitalization. A heading starts with a capital, but other words should not be capped up, unless they are proper nouns. If in doubt, choose lower case.
Exceptions include: our Sun, Earth (the planet), and our Solar System, but not universe, moon, earthquake, earth (the soil).
Use a capital letter when you are writing the names of people, languages, places, and words relating to them: