List of 20 hardest words to spell?

There's no definitive list of "hardest words" because difficulty is subjective and depends on the individual's language background and experience. However, here's a list of 20 words often cited as being challenging to spell, due to their unusual letter combinations, silent letters, or multiple pronunciations:

General Difficulty:

1. Pneumonoultramicroscopicsilicovolcanoconiosis: The longest word in the English language, describing a lung disease caused by inhaling very fine silica dust.

2. Queue: This word has a silent "u" and is often confused with "cue."

3. Rhythm: The "th" and "ym" combinations can be tricky.

4. Eerie: The double "e" and silent "e" are easily mispronounced.

5. Aerie: This word, meaning a bird's nest high up, has a silent "e" and is often confused with "airy."

6. Supercalifragilisticexpialidocious: A nonsensical word from Mary Poppins, but nonetheless a challenge to spell!

7. Indispensable: This word has a few unusual letter combinations.

8. Conscientious: The double "s" and the "ti" combination can be tricky.

9. A lot: This two-word phrase is often incorrectly written as "alot."

10. Embarrass: This word is often misspelled as "embarass."

11. Mischievous: The "ie" combination is often mispronounced.

12. Cemetery: The "e" at the end is silent and often omitted.

13. February: The "u" is often forgotten.

14. Definitely: The double "f" and "n" combinations are easily overlooked.

15. Foreign: The silent "e" is often forgotten.

16. Parallel: The double "l" and the "ar" combination can be tricky.

17. Believe: The "ie" combination is often mispronounced.

18. Separate: This word is often misspelled as "seperate."

19. Sacrilegious: The "g" is silent and often forgotten.

20. Accommodate: This word is often misspelled as "acommodate."

Remember: Everyone struggles with different words. The best way to improve your spelling is to read widely, use a dictionary when unsure, and practice writing frequently.