Questions & Answers about Я сравниваю оба варианта.
Why do we use оба варианта instead of a plural form for 'options'?
In Russian, the word оба (both) behaves grammatically like the number два (two). When used in the Nominative case or as an inanimate Accusative object, it forces the following noun into the Genitive singular instead of a plural form. So, the masculine noun вариант becomes варианта.
How do I know whether to use оба or обе here?
It depends on the gender of the noun. вариант is masculine, so it takes оба. If you were comparing two feminine nouns, like книга (book), you would use обе followed by the Genitive singular: обе книги. Neuter nouns also use оба.
Since оба варианта is the direct object of the verb, why isn't it taking a special Accusative ending?
It actually is in the Accusative case! Because вариант is an inanimate noun, the Accusative forms for both the quantifier (оба) and the noun phrase as a whole look exactly like the Nominative. If you were comparing two living things, like 'both brothers', you would have to use the animate Accusative form: обоих братьев.
Are there any helpful tricks for remembering the verb сравнивать (to compare)?