Physics base units help?

Question

In my notes, it says : Base units - express fundamental quanities; can be primary (second) or seconday (hour).

What is primary and secondary ?

Answer 1

There are 7 primary quantities and units:

1. length

    meter: m

2. mass

    kilogram: kg

3. time

    second: s

4. electric current

    ampere: A

5. thermodynamic temperature

    kelvin: K

6. amount of substance

    mole: mol

7. luminous intensity

    candela: cd

All other units are secondary. They are conversions or combinations of the primary units.