In a scientific name,what taxonomic category does the second word represent?

The science of naming plants is known as

The International Code of Botanical Nomenclature $(ICBN)$ has provided a code for the classification of plants. Provide the hierarchy of units of classification that botanists follow while classifying plants and mention the different 'suffixes' used for these units.

Write a short note on taxonomic categories.

Which of the following is less general in characters as compared to genus?

$A :$ Members of a species are reproductively isolated from the members of other species.
$R :$ Species is the basic taxonomic category.