Why do we need Scientific names instead of common names?

Scientific names are formal, universally accepted names that obey rules and regulations for naming of plants and animals provided by the International Code of Botanical Nomenclature (ICBN) or International Commission on Zoological Nomenclature (ICZN). Binomial nomenclature system is followed in which a scientific name has two parts or epithets; generic epithet and specific epithet followed by author citation (Abbreviation of the author who published the name first). Author citation is optional but often advisable. Eg: Mangifera indica Linn. for mango tree.

Why we need scientific names instead of vernacular or common names?

Limitations of common names

An organism can have multiple common names
Vary from country to country or within state or locality.
Known by people of one region, language or country
Name available for only relatively few plant and animal species
Not universal, not regulated by any constituted authority
Non specific and often misleading “ring worm” is not a worm. It is a fungus. Jelly fish is not a fish

Why scientific names are useful in taxonomy?

An universally accepted name and understood globally
Each organism identified has a unique scientific name
Scientific name seldom changes
Scientific names are often descriptive and logical and suggest some information about animal or a plant. Example: Thunbergia grandiflora (grandiflora=large flowered)