Is sunflower a herb or shrub?

First let us know the difference between shrub and herb:

1. Herbs are shorter than shrubs.
2. Herbs don't have multiple stems while shrubs have multiple branches.
3. There are about 3 groups of herbs while there are four groups of shrubs.
4. Herbs can be grown beneath the shrubs whereas shrubs cannot be grown in such a way.
5. Herbs are called as rootstock whereas herbs are referred to as woody plant.

Accordingly, The common sunflower is an annual herb with a rough hairy stem 1-4.5 metres high, broad, coarsely toothed, rough leaves 7.5-30 cm long, and heads of flowers 7.5-15 cm wide in wild specimens and often 30 cm or more in cultivated types.