Alyosha & Zosima

Среди миров, в мерцании светил

1. Среди миров: preposition “среди” (= among) + plural (translated as a singular here) genitive of masculine “мир” (= universe / world; peace)
2. в мерцании: preposition “в” (= in) + singular prepositional (position, no movement) of neutral “мерцание” (= twinkling, universe)
3. светил: plural genitive of neutral “светило” (= luminary, star), complement of noun “мерцание”

Одной звезды я повторяю имя.
Alternative syntax: я повторяю имя одной звезды

1. я повторяю: personal nominative pronoun “я” + present of imperfective “повторять” (= repeat)
2. имя одной звезды: singular accusative of neutral “имя” (not a feminine noun, same declension as “время”), singular genitive of feminine determiner “один” and noun “звезда”

Не потому, чтоб я ее любил,

1. Не потому, чтоб: negation “не”, “потому, чтоб” = because
2. я ее любил: feminine accusative personal pronoun “её” (corresponding to “она” = she), present of imperfective “любить” (= love)

А потому, что мне темно с другими.

1. А потому, что: conjunction “а” (= but)
2. мне темно: impersonal syntax (no subject in the nominative case). Dative of personal pronoun “мне” (corresponding to “я”), predicative adverb “темно” (= it is dark)
3. с другими: preposition “ с” (= with), plural instrumental of determiner pronoun “друг” (not the declension of “друг друга” = each other)

И если мне на сердце тяжело,

1. И если: conjunction “и” (and), conditional “если” (= if)
2. мне на сердце тяжело: impersonal syntax. Preposition “на” (= on), singular prepositional of neutral “сердце” (= heart), predicative adverb “тяжело” (= it is hard / painful / distressing)

Я у нее одной ищу ответа,
Alternative syntax: Я ищу ответа у нее одной

1. Я ищу ответа: first person, present of imperfective “искать” (= look for), a verb listed as commanding the genitive at masterussian.net, singular genitive of masculine “ответ” (= reply, answer)
2. у нее одной: preposition “у” (+ at, by), singular genitive of feminine 3rd personal pronoun “её” and determiner “один” (only, one)

Не потому, что от нее светло,

1. от нее светло: impersonal syntax. Preposition “от” (from), singular genitive of feminine 3rd personal pronoun “её”, predicative adverb “светло” (= it is light / daylight)

А потому, что с ней не надо света

1. с ней: preposition “с” (= with), singular instrumental of feminine “ей” (“н” added, if not already present, to some declensions of the 3rd person pronoun after a preposition, for phonetic reasons, if ruled directly by the preposition)
2. не надо света: impersonal syntax. Predicative adverb “надо” (= it is necessary, need), singular genitive of masculine “свет” (= star) because of the negation

• The noun “звезда” is feminine in Russian. The strict translation of the corresponding pronoun in English is expected to be “it” for an object. A French translation would have kept the gender. But a decision had to be made in English whether to make the personifying of the “star” apparent or not, hence the “she”, which lets the image show without, hopefully, making the literary device too self-conscious and thus distracting.
• The plural genitive of masculine “мир” (= universe / world; peace) was translated as a singular here.
• потому, чтоб (чтобы) / потому, что: I have not been able to find any references to the distinction between чтоб and что in association with “потому”.
• The translation I have come up with sounds a bit ornamental. Overall, though, the Russian language is more concise, precise and comes with more unobtrusive but decisive nuances than English. For example, the following phrase, unrelated to our present text, “Жить за городом” literally means “to live on the outskirt of / beyond the city”, that is “to live in the suburbs / country”, without the need for a specific noun either for “suburb” or “country”. The preposition “за” was enough to transmute the meaning of the phrase where a preposition like “в” would have meant “in the city”.
• The conciseness mentioned above owes much to the rich declension system with its six cases. This apparent complexity makes room for more freedom in the syntax, more indeed than in German, in spite of the similar declension system of this latter. Liberated from the necessity to assign functions to elements of the sentence, the syntax or word order can be used to convey perspective or style. Periphrases, and thus possibly longer sentences, have to be made up to express the speaker’s emphasis on particular parts of the speech in English, though here word stresses will often do when speaking.