还是从词性入手谈比较好：
区别：
1.free可以作形容词，而freely只作副词。Free形容词用法如下：
1）自由的，无约束的；能随自己意愿的；随心所欲的
The new treaty establishes a free trade zone.
新条约设立了自由贸易区。
They gave me free access to all the files.
他们让我自由查阅所有档案资料。
A true democracy complete with free speech and a free press was called for.
人们呼吁要有充分言论自由和新闻自由的真正民主。
The government will be free to pursue its economic policies...
政府将可不受限制地实行其经济政策。
Students have a free choice of courses in their final year.
学生在最后一学年可以自由选修课程。
I have no ambitions other than to have a happy life and be free.
我没有雄心大志，只求自由自在地过幸福生活。
You are free to come and go as you please.
你来去自由。
He walked from the court house a free man.
他以自由之身走出了法院。
You’re free to choose your major.你可以自由选择你的专业。
He fears that until state subsidies are removed, Russia will never have a truly free press
他担心在取消国家补助之前，俄罗斯将根本不会有真正自由的媒体。
Ensure there is a free flow of air around the machine.
要确保机器周围空气畅通。
A free trade agreement would be advantageous to both countries.
自由贸易协定对两国都会有利。
She was a supporter of the free market economy.
她是自由市场经济的拥护者。
2）时间或空间上空闲的，未被占用的
Will you be free this morning?
你今天上午有空吗？
I dont have much free time.
我没有多少空闲时间。
Do you have much free time?
你空闲时间多吗？
She spent her free time shopping.
她空闲的时候就去购物。
There was only one seat free on the train.
列车上只剩下一个空座。
He held out his free hand and I took it.
他伸出空着的一只手，我就抓住了。
There will be no rooms free in the hotel until after the holidays.
要在假期过后才有空房间。
The job was beginning to make unreasonable demands on his free time.
他的闲暇时间开始被工作过分地侵占了。
3）免费的，无偿的
We enjoy medical care.我们享受免费医疗。
Admission to the concert is free.音乐会免费入场。
Were offering a fabulous free gift with each copy you buy.
购买一册就可以得到一份免费好礼。
Delivery is free of charge.
免费送货。
The seminars are free, with lunch provided.
研讨会不收会务费，而且还提供午餐。
Free newspapers: please take one.
报纸免费，请取一份。
Medical care is still free at the point of use.
医疗保健在实际提供点仍然是免费的。
There has been a high uptake of the free training.
免费培训有很多人参加。
The school funds a set number of free places.
学校资助固定数目的免费生。
The state provides free education.
政府提供免费教育。
Pick up one of our free information sheets at reception.
请在接待处拿一份我们的免费资料。
You will automatically get free dental treatment if you are under 18.
18岁以下的人一律免费得到牙科治疗。
Can you work it so that we get free tickets?
你能不能为我们搞到些免费票？
We offer customers a free home delivery service.
我们为客户提供免费送货上门的服务。
4）be free from/of
某某没有……的，摆脱了……的；不含有害物的；不受…伤害（或影响等的）:
It was several weeks before he was completely free of pain.
过了几星期他的疼痛才完全消除。
At last he was free from the financial bloodsuckers.
最后他终于摆脱了那些吸金者的经济剥削。
Given data which are free from bias there are further snares to avoid in statistical work
即使数据本身不存在偏差在统计工作中仍需要避免其他陷阱。
She is free from care.
她无忧无虑。
Probably no one is free from mistakes, only some make more and some less.
人大概没有不犯错误的，多多少少要犯错误。
No human being can be free from mistakes.
是人总要犯错误。
He is free from any bias.
他丝毫不偏心。
This dictionary, despite the care exercised in compiling it, cannot in the nature of things be free from error.
本词典虽非草率之作，但错误仍在所难免。
I loved being free from the Internet, and I really didnt mind not having updates about what my friends were doing.
我喜欢远离互联网，我真的不介意我的朋友们在做什么。
中考真题- 2016 河南
They envision an equal society, free of poverty and disease.
他们向往一个没有贫穷和疾病的平等社会。
Never had he been so free of worry
他从未如此无忧无虑过。
The marriage was a failure and they both wanted to be free of it
他们的婚姻很失败，两人都想摆脱它。
This government is not entirely free of suspicion.
这个政府并非完全不受置疑。
2.作为副词区别如下：
1）free主要表示免费的,位于动词之后，如：
You can eat free in my restaurant whenever you like.
你可以在你喜欢的时候来我的饭店免费消费。
Children under five travel free.
五岁以下儿童乘客免费。
I wasnt expecting you to do it for free.
我并没有指望你白干。
The books are given away free.这些书是免费赠送的。
Children are admitted free.儿童免费进场。
The newspaper is distributed free.本报免费发送。
The sick were allowed to pass free.病人可以免费通过。
Children can get into the museum free.儿童可以免费进入博物馆参观。
You can travel free with this special ticket.你用这张特别的票可以免费旅游。
Free作为副词，表免费地，在口语中通常可以用介词短语for free代替：
My neighbor cut my hair free.=
My neighbor cut my hair for free.
我的邻居免费给我理发。
另外free of charge也表示免费:
The company will deliver free. =
The company will deliver free for charge.
公司免费送货上门。
The computer is still under guarantee, so you should be able to get it repaired free of charge.
电脑仍在质保期，所以你可以免费获得维修。
2)freely 副词，自由地，随便地，无限制地，无阻碍地，顺畅地，主动地，心甘情愿地，慷慨地，公开地，坦率地，公开地，坦率地
可以位于动词之前或之后：
EU citizens can now travel freely between member states.
欧盟国家的公民现在可以在成员国之间自由旅行。
They cast their votes freely and without coercion on election day...
选举日那天他们自由地进行了投票，没有受到胁迫。
Merchandise can now circulate freely among the EU countries.
商品现在可以在欧盟各国自由流通。
Water flowed freely from the pipe.
水从管道里通畅地流了出来。
When the gate is raised, the water can flow freely.
闸门提起时水就可以畅流。
The clay court was slippery and he was unable to move freely...
红土网球场很滑，他不能自如地移动。
Traffic is now moving more freely following an earlier accident.
早些时候的交通事故过后，现在交通通畅些了。
The book is now freely available in the shops.
现在这本书在商店可以随时买到。
The wine flowed freely.
葡萄酒无限量供应。
You may speak freely.你可以直言。
You may speak freely; say what you like.
你可以自由讲话，想说什么说什么。
He could write freely about it now.
他可以自由地写这个问题了。
I freely admit that I made a mistake.
我心甘情愿(爽快)地承认我弄错了。
I freely admit that what I said at the meeting was wrong.
我主动承认刚才在会上讲的话是错了。
Danny shared his knowledge freely with anyone interested.
丹尼十分乐意地和所有感兴趣的人分享他的知识。
Millions of people gave freely in response to the famine appeal for the victims of the earthquake.
为响应救济地震灾民的呼吁，几百万人慷慨相助。
It may require courage to speak freely.
要有勇气，才能直言不讳。（公开地，坦率地）