Nomenclature and Taxonomy
Sweet basil, Ocimum basilicum (O. basilicum), has multiple cultivars. Thai basil, or O. basilicum 'Horapha', grows to 45 cm (1.48 ft) in height, and has purple-flushed, lance-like leaves with a sweet licorice scent.
The word Ocimum is derived from the Greek word meaning "to smell", which is appropriate for most members of the plant family Lamiaceae, also known as the mint family. Like other plants in the mint family, Thai basil features a square stem, and the leaves always grow in pairs, opposite each other and at 90 degree angles from the previous pair of leaves. With over 40 cultivars of basil, this abundance of flavors, aromas and colors leads to confusion when identifying specific cultivars. For a detailed comparison, see Purdue University's O. basilicum research and Sunland Herb's anecdotal descriptions of basil, based on four historical resources.
Read more about this topic: Thai Basil