The most commonly used letters in different languages vary based on the frequency of letters in their respective alphabets. Here’s a breakdown by country, based on the dominant language spoken:

English (USA, UK, Canada, Australia, etc.)

• Most common letter: E
• Other frequent letters: T, A, O, I, N, S, H, R

Spanish (Spain, Latin America)

• Most common letter: E
• Other frequent letters: A, O, S, R, N, I, D

French (France, Canada, Belgium, etc.)

• Most common letter: E
• Other frequent letters: A, I, S, N, R, T

German (Germany, Austria, Switzerland)

• Most common letter: E
• Other frequent letters: N, I, S, R, A, T, D

Italian (Italy)

• Most common letter: E
• Other frequent letters: A, I, O, N, R, T, L

Portuguese (Portugal, Brazil)

• Most common letter: A
• Other frequent letters: E, O, S, R, I, D

Russian (Russia, parts of Eastern Europe)

• Most common letter: О (O)
• Other frequent letters: Е (E), А (A), И (I), Н (N), Т (T), С (S)

Chinese (Mandarin, China, Taiwan, Singapore)

• Since Chinese is logographic, letter frequency isn’t relevant, but the most common characters include:
  • 的 (de) (possessive particle)
  • 一 (yī) (one)
  • 是 (shì) (to be)

Arabic (Middle East, North Africa)

• Most common letter: ا (Alif – equivalent to “A”)
• Other frequent letters: ل (L), م (M), ن (N), ي (Y), هـ (H)

Hindi (India)

• Most common letter: आ (Ā)
• Other frequent letters: क (K), त (T), म (M), न (N)

Japanese (Japan)

• For kana scripts, the most common characters in hiragana:
  • い (I), ん (N), か (Ka), し (Shi)
• In kanji, frequently used characters include:
  • 日 (sun/day), 本 (origin/book), 人 (person)

Turkish (Turkey)

• Most common letter: A
• Other frequent letters: E, I, N, R, K, L

Polish (Poland)

• Most common letter: A
• Other frequent letters: E, O, I, N, S, T, R

Dutch (Netherlands, Belgium)

• Most common letter: E
• Other frequent letters: N, A, T, I, O, R

Swedish (Sweden)

• Most common letter: E
• Other frequent letters: A, T, R, N, I, S

Finnish (Finland)

• Most common letter: A
• Other frequent letters: I, T, N, E, S, K

Greek (Greece)

• Most common letter: Α (A)
• Other frequent letters: Ε (E), Ο (O), Ν (N), Ι (I), Σ (S), Τ (T)

Across most languages, vowels such as E, A, and O tend to be the most commonly used letters. However, some languages, like Russian, Arabic, and Chinese, have different structures that influence letter frequency.