1) The Druids were the Priests, Priestesses and Magicians of the Celtic people. They administered religion, justice and education. Don't put capitals on three of these words -- which three, do you think? Also, you need a comma after "justice."
2) The word “Druidae” is of Celtic origin and combines the root words “oak” and “knowledge”. The oak, along with the mistletoe, was the most important sacred tree to the Druids.
3)In the Celtic social system, Druid was a title given to learned men and women possessing “oak knowledge” or “oak wisdom”. OK
4) According to mythologies, they could predict the future, control the weather and transform themselves into the forms of animals . <~~delete the extra space before the period; you also need a comma after "weather."
5) Many Druids were women. Unlike women in other contemporary cultures, they enjoyed more freedom and were entitled to enter battle and divorce their husbands.
6) The black death spread because of the primitive, dirty, and unhealthful living conditions, as well as the lack of sanitation. Be sure to look up the difference between "healthy" and "healthful"!!
7) It brought about a rise in the mortality rate, a shortage of labour, an increase in wages and a fall in prices. Comma needed after "wages."
8) Anticlericalism developed in the 14th century for three main reasons: It criticised the corruption in monastic orders which lent money at interest, the wealth of the Clergy, which presented itself in the role of feudal lord, living in power and luxury.
I see only two reasons: criticizing corruption and wealth. What's the third?
I forgot to include the following statements. I really hope you can check them, too
1) The Druids were the Priests, Priestesses and Magicians of the Celtic people. They administered religion, justice and education.
2) The word “Druidae” is of Celtic origin and combines the word roots “oak” and “knowledge”. The oak, along with the mistletoe, were (was?) the most important sacred trees to the Druids.
3)In the Celtic social system, Druid was a title given to learned men and women possessing “oak knowledge” or “oak wisdom”.
4) According to mythologies, they could predict the future, control the weather and shape-change themselves into the forms of animals .
5)Many Druids were women. Unlike women in other contemporary cultures, they enjoyed more freedom and were entitled to enter battle and divorce their husband.
6) The black death spread because of the primitive, dirty, and unhealthy living conditions and the lack of sanitation.
7)It brought about a rise in the mortality rate, a shortage of labour, an increase in wages and a fall in prices.
8) Anticlericalism developed in the 14th century for three main reasons. They (it) criticised the corruption in monastic orders which lent money at interest, the wealth of the Clergy, which presented itself in the role of feudal lord, living in power and luxury.
2 answers
In #4, you could also use "change" instead of "transform" if you wish.