1. He is of medium height.

2. He is of average weight.
3. He has medium height.
4. He has average weight.
5. He has long curved hair.
6. She has short straight blond hair.
7. She has medium-length wavy blonde hair
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Are all the sentences grammatical?
Would you check them and correct errors, please.

1 is OK.

2 is OK.
3 is not OK.
4 is not OK.
5 is OK if you delete "curved" and insert "wavy."
5 is OK.
6 is OK if you put a period at the end.

You might need commas with the adjectives in 5 and 6. Check here to see:
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1. He is of medium height. (Correct grammar)

2. He is of average weight. (Correct grammar)
3. He has medium height. (Should be rewritten as "He has a medium height.")
4. He has average weight. (Should be rewritten as "He has an average weight.")
5. He has long curved hair. (Should be rewritten as "He has long, curly hair.")
6. She has short straight blond hair. (Correct grammar)
7. She has medium-length wavy blonde hair. (Correct grammar)

All of the sentences you provided are grammatically correct. However, there are a few suggestions for improvement:

1. He is of medium height.
2. He is of average weight.
3. He has medium height.
4. He has average weight.
5. He has long, curly hair.
6. She has short, straight, blond hair.
7. She has medium-length, wavy, blonde hair.

In sentences 5, 6, and 7, I added commas to separate the adjectives for better clarity. Additionally, in sentence 5, I changed "curved" to "curly" as it is a more common term for describing hair texture.