Why is GRE's words so difficult to memory?

Why is GRE's words so difficult to memory? an essay explains why grammer is more important than vacabulary and it's more than250 words GRE word list is too difficult to memory.I have tried to memory GRE for 40 times,there arestill some words that I haven't mastered.Why? There is no why,it`s an There is a s( ) difference between these two words Mother's words,that is always right如何翻译 英语翻译take Pam's words That's why it is called:The Present是什么意思? that is why it's called the present. Which little pig 's house is the best?Why? no one is perfect,that's why pencils have erasers, it ,s i in happiness ,there is no why Do you think a person's name is important why? 翻译:where is paul,bob?he's playing football,why? Why is John's little brother ill in bed? why is a person's dress important in business communication why is the letter s like a thunder Why is the letter S like thunder(雷声）?