Because the Russian language borrowed some terms from other languages, there are various conventions for sounds that are not present in Russian.
For instance, while the Russian language does not include [h], there are a few common words (particularly proper nouns) borrowed from languages like German and English that contain a particular sound in the original language. In well-established terms, like галлюцинация [ɡəlʲʊtsɨˈnatsɨjə] ('hallucination'), this is written with ⟨г⟩ and pronounced with /ɡ/, while more recent terms use ⟨х⟩, pronounced with /x/, like as хобби [ˈxobʲɪ] ('hobby').
Similarly, words that initially include [θ] in their source language are usually pronounced with /t(ʲ)/), as in the name Тельма ('Thelma') or, if borrowed early enough, with /f(ʲ)/ or /v(ʲ)/, as in the names Матве́й ('Matthew') and Фёдор ('Theodore').
For the [d͡ʒ] affricate, which is popular in the Asian countries that used to be parts of USSR and the Russian Empire, the letter combination ⟨дж⟩ is typically used. In essence, this is frequently transliterated into English either as ⟨dzh⟩ or the Dutch form ⟨dj⟩.
The numerical values correspond to the Greek numerals, with ⟨ч⟩ being used for koppa, ⟨ц⟩ for sampi, and ⟨ѕ⟩ for digamma. In 1708 the system was abandoned for secular purposes after a transitional period of a century or so. However, it continues to be used in Church Slavonic, while standard Russian texts use Roman numerals and Hindu-Arabic numerals.
There are several variations of so-called "phonetic keyboards" that are frequently used by non-Russians, where, as far as is possible, pressing an English letter key will type the Russian letter with a similar sound (A → А, D → Д, S → С, F → Ф, etc.).
Russian spelling uses fewer diacritics than it is common for most European languages. The only diacritic, in the proper sense, is the acute accent ⟨◌́⟩ (Russian: знак ударения 'mark of stress'), which indicates stress on a vowel, as it is done in Greek and Spanish. Russian word stress can be described as unpredictable and can fall on different syllables in different forms of the same word. The diacritic is used only in children's books, resources for foreign-language learners, dictionaries, the defining entry (in bold) in articles on Wikipedia, or on minimal pairs distinguished only by stress (for example, за́мок 'castle' vs. замо́к 'lock'). Seldom, it is used to define the stress in uncommon foreign words and in poems with unusual stress used to fit the meter. Unicode does not include code points for the accented letters; they are instead produced by suffixing the unaccented letter with U+0301 ◌́ combining acute accent.
The letter ⟨ё⟩ represents a specific version of the letter ⟨е⟩, which is not always distinguished in written Russian; however, it has no other uses. Stress on this letter is never marked because it is always stressed except in some loanwords.
Unlike the case of ⟨ё⟩, the letter ⟨й⟩ is wholly separated from ⟨и⟩. It has been actively used since the 16th century except for the period from 1708 to 1735 when it was removed. After 1735, its usage has been obligatory. It was previously considered a diacriticized letter, but in the 20th century, it came to be regarded as a separate letter of the Russian alphabet. 19th- and 20th-century grammarians classified it as a "semivowel"; however, after the 1970s, it has been considered a consonant letter.