What is the botanical nemes of green chilli?

Answer 1

All chili peppers, from bland sweet bell peppers to Guatemalan insanity peppers that will melt your tongue at twelve paces, are in the genus Capsicum. For that matter, there are only five domesticated species; bell peppers, jalapenos, serranos, Anaheim, and poblanos are all different cultivars (if you think "like Dog Breeds, but with plants" you won't be far off) of Capsicum annuum, and the small Thai peppers and Tabasco peppers are both Capsicum frutescens. The hottest peppers (habaneros, datils) are usually Capsicum chinense.

If you want an exact species name, you need to be more specific than "green chili"; most chili peppers are green when not fully ripe.