"Goal" is about something important that you hope to achieve in the future and usually something bigger or long-term achievement. It is usually just a noun.
“Goal”是指你希望在未来实现的重要目标，通常是更大或长期的目标。它通常只作名词。
Set your goals to help you achieve your dream in 2018.设定目标，帮助你在2018年实现梦想。Her goal was to get an A grade in her English test.她的目标是在英语考试中获得A级。The country can still achieve its goal of reducing poverty by a third.这个国家仍然可以实现减贫三分之一的目标。"Aim" also means something you hope to achieve but it should be something more short term, also it can be both a Verb or a Noun.
“Aim”也意味着你希望达到的目标，但它一般是短期的目标，可以作动词（目的是，旨在）或名词（目标）。
I am aiming for the champion. (Verb)我旨在拿冠军。（动词）what’s your aim? (Noun)你的目标是什么？（名词）The main aim of the plan was to provide employment for local people.该计划的主要目的是为当地人民提供就业机会。"Purpose" is more likely the reason/motive (why) someone are doing something.
“Purpose ”偏向于表示某人做某事的原因/动机（目的）。
my purpose of this class is to learn about the renaissance era. 我上这门课的目的是了解文艺复兴时期。This messages purpose is to teach you the difference.这些信息的目的是教你区别。现在你们会区分了吗？
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