區別一：free 可以用作形容詞，但freely 不可用作形容詞。free 用作形容詞主要用法如下：
1. 自由的，無約束的
You are free to go or stay as you please. 你可以走也可以留下，隨你便。
You’re free to choose your major. 你可以自由選擇你的專業。
2. (時間或空間)空閒的，未被占用的
Will you be free this afternoon? 你今天下午有空嗎？
There will be no rooms free in the hotel until after the holidays.
要在假期過後旅館中才有空閒的房間。
3. 免費的，無償的
You can eat free in my restaurant whenever you like.
你可以在任何時候來我們飯店免費用餐。
We enjoy free medical care. 我們享受免費醫療。
Admission to the concert is free. 音樂會是免費入場的。
4. 無…的，擺脫了…的
This district is free from air pollution. 這個地方是沒有空氣污染的。
The secretary was free from all blame for the errors. 這些失誤完全不能怪秘書。
區別二：free 與 freely 都可用作副詞，但有區別：
1. free 主要表示「免費地、自由地」。如：
The newspaper is distributed free. 本報免費發送。
The sick were allowed to pass free. 病人可以免費通過。
Children can get into the museum free. 兒童可以免費進入博物館參觀。
Children under five travel free.
五歲以下兒童乘客免費。
You can travel free with this special ticket. 你用這張特別的票可以免費旅行。
Buy two CDs and get another completely free. 購買兩張雷射唱片即可免費獲贈一張。
The children ran free across the meadow.
孩子們自由地在草地上奔跑。
副詞free一般位於動詞之後。
2. 副詞 freely 的主要用法有：（freely副詞一般位於動詞之後或之前也可以。）
(1) 不受限制地，自由地
EU citizens can now travel freely between member states.
歐盟國家的公民現在可以在成員國之間自由旅行。
Now that we are alone, we can speak freely. 現在我們單獨在一起，可以隨便談了。
Conversation flowed freely when the speaker invited discussion. 演講人請大家討論，於是人人暢所欲言。
They cast their votes freely and without coercion on election day.
選舉日那天他們自由地進行了投票，沒有受到脅迫。
Merchandise can now circulate freely among the EU countries.
商品現在可以在歐盟各國自由流通。
59 per cent of people believed the pound should be allowed to float freely.
59%的人認為應該允許英鎊自由浮動。
The princess was not recognized and mingled freely with the crowds.
公主沒有人認出，隨意混雜在人群之中。
They move freely from one department to another as they ascend the civil service ladder.
隨著仕途晉升，他們可以在部門間隨意調動。
The book is now freely available in the shops.
現在這本書在商店可以隨時買到。
They used these words freely, often in front of their parents too.
這些語詞他們隨口即出，在父母面前也常常如此。
The sheep are allowed to roam freely on this land.
綿羊可以在這片地上自由走動。
(2) 不受干擾地，通暢地，無阻地
Water flowed freely from the pipe. 水從管道里通暢地流了出來。
Conversation flowed freely throughout the meal.
席間大家一直談笑甚歡。
Troops would patrol major roads to ensure that traffic flows freely throughout the country.
軍隊將在主要道路巡邏以確保全國的交通通暢。
When the gate is raised, the water can flow freely.
閘門提起時水就可以暢流。
Traffic is now moving more freely following an earlier accident.
早些時候的交通事故過後，現在交通通暢些了。
The clay court was slippery and he was unable to move freely...
紅土網球場很滑，他不能自如地移動。
If they cannot do this, they have not really learned the spirit of the foreign language and cannot use it freely.
如果做不到這一點，他們就沒有真正掌握外語的本質，因而不能運用自如。
(3) 主動地，自願地，樂意地
I freely admit that I made a mistake.
我爽快地承認我犯了錯誤。
Danny shared his knowledge freely with anyone interested.
丹尼十分樂意地和所有感興趣的人分享他的知識。
I freely admit that what I said at the meeting was wrong. 我主動承認剛才在會上講的話錯了。
(4) 慷慨地，大方地，毫無保留地，
I freely give it to you.
我毫無保留地把它給你。
Millions of people gave freely in response to the famine appeal. 千百萬人響應救災呼籲而慷慨解囊。
(5) 根據大意地，非逐字逐句地
Poems have to be translated quite freely. 詩歌只能根據意思來靈活翻譯。
(6) 公開地，坦率地，無顧忌地
It may require courage to speak freely. 要有勇氣才能直言不諱。
For the first time he was able to speak freely without the fear of reprisals against his family.
他第一次能夠直言不諱而不怕家人遭到報復。
You may speak freely; say what you like.
你喜歡說什麼儘管可以直言不諱。
She wondered whether he had someone to whom he could talk freely.
她不知道他是否有可以傾心交談的對象。
He freely admits he is unemployable and will probably never find a job.
他坦率地承認自己沒什麼技能，可能永遠也找不到一份工作。
It will be difficult for her to open out and discuss her problems freely with you.
她將很難敞開心扉跟你無拘無束地討論自己的問題。
（7）經常地;大量地
We have referred freely to his ideas...
我們頻繁地提到了他的觀點。
說明：free 用作副詞表示「免費地、自由地」，在口語中通常可用介詞短語 for free 代之。如：
My neighbour cut my hair for free. 我的鄰居免費給我理髮。
I got this ticket for free from somebody who didn't want it. 我這張票沒花錢，是別人不要的。
We might be able to get some plants for free. 我們或許能免費得到一些樹苗。
It would be unreasonable to expect them to do all that work for free. 期待他們不計報酬完成所有那些工作簡直是不合情理的。
另外，free of charge 也表示「免費」。如：
The company will deliver free of charge. 公司免費送貨上門。
We will send you our booklet free of charge. 我們將免費寄送小冊子給你。
The car is still under guarantee, so you should be able to get it repaired free of charge. 汽車仍處於質保期內，你可以免費獲得維修。