In botany and Ayurveda, what is the widely used scientific name of the holy basil plant that is commonly known in India as Tulsi?

Introduction / Context:
Tulsi, or holy basil, is an important medicinal and sacred plant in India. Many general science and biology questions test your memory of the scientific names of commonly known plants. This question asks you to connect the familiar name Tulsi with its correct botanical name.

Given Data / Assumptions:
• The common name is Tulsi, also called holy basil.
• The question asks for the scientific name, which follows binomial nomenclature with a genus and species name.
• Options include scientific names of several unrelated plants such as cotton, maize and neem.

Concept / Approach:
In binomial nomenclature, each plant species is given a Latin or Latinised name. Holy basil, commonly called Tulsi, belongs to the genus Ocimum. The traditional and widely used scientific name is Ocimum sanctum, although some modern literature uses Ocimum tenuiflorum. The other options belong to very different plants: Gossypium herbaceum is a cotton plant, Zea mays is maize or corn, Cajanus cajan is pigeon pea, and Azadirachta indica is neem.

Step-by-Step Solution:
Step 1: Recall that Tulsi is a species of basil, and basil plants belong to the genus Ocimum. Step 2: Remember that the classical scientific name used in many exam books for holy basil is Ocimum sanctum. Step 3: Compare with Gossypium herbaceum, which is clearly associated with cotton cultivation, not Tulsi. Step 4: Zea mays refers to maize, a cereal crop, and Cajanus cajan refers to pigeon pea, a pulse crop. Step 5: Azadirachta indica is neem, a different medicinal tree, so the only matching name is Ocimum sanctum.

Verification / Alternative check:
Ayurveda and botany texts list Tulsi or holy basil as Ocimum sanctum, and many traditional medicine preparations use this name. Exam oriented general science books also repeat this pairing, which confirms that Ocimum sanctum is the expected answer in such multiple choice questions.

Why Other Options Are Wrong:
Gossypium herbaceum: This is an Old World cotton species, cultivated for fibre, unrelated to Tulsi.
Zea mays: Scientific name for maize or corn, a cereal crop and not a medicinal herb like Tulsi.
Cajanus cajan: Botanical name of pigeon pea or arhar dal, a legume crop.
Azadirachta indica: Scientific name for neem, an important medicinal and insecticidal tree but not Tulsi.

Common Pitfalls:
The main difficulty here is remembering many similar sounding Latin names. Students sometimes confuse Tulsi with neem because both have religious and medicinal significance. To avoid this, link Ocimum sanctum specifically to basil leaves used in herbal remedies and rituals, while remembering that Azadirachta indica is a larger tree known for bitter leaves and neem oil.

Final Answer:
The scientific name widely associated with Tulsi or holy basil is Ocimum sanctum.