Context: Russian distinguishes between consonant phonemes with palatal secondary articulation and those without, the so-called soft and hard sounds. This distinction is found between pairs of almost all consonants and is one of the most distinguishing features of the language. Another important aspect is the reduction of unstressed vowels. Stress, which is unpredictable, is not normally indicated orthographically though an optional acute accent (знак ударения, znak udareniya) may be used to mark stress, such as to distinguish between homographic words, for example замо́к (zamok, meaning a lock) and за́мок (zamok, meaning a castle), or to indicate the proper pronunciation of uncommon words or names.

Question: What kind of phonemes are soft sounds?
Answer: consonant phonemes with palatal secondary articulation

Question: What kind of accent can mark stress?
Answer: optional acute accent

Question: What kind of words can acute accents distinguish?
Answer: homographic words

Question: What word means both lock and castle, depending on its accent?
Answer: zamok

Question: What kind of phenomes are uncommon words?
Answer: Unanswerable

Question: Where are uncommon words usually found?
Answer: Unanswerable

Question: What feature of the language is an uncommon word considered?
Answer: Unanswerable

Question: What are uncommon words or names considered to be and not usually indicated?
Answer: Unanswerable

Question: What is an uncommon word used to mark?
Answer: Unanswerable