Kate's Blog

logo    （某公司或機構的）標識，標誌，徽標 

               a printed design or symbol that a company or an organization uses as its special sign 

A logo is a graphic mark or emblem commonly used by commercial enterprises, organizations and even individuals to aid and promote instant public recognition. In plainer words a logo is a symbol that represents a company. ...
en.wikipedia.org/wiki/Logo

http://www.google.com.tw/dictionary?langpair=en|zh-TW&q=logo&hl=zh-TW&aq=f

mark   符號；記號；（顯示質量所有者等的）標記

a written or printed symbol that is used as a sign of something, for example the quality ofsomething or who made or owns it 

http://www.google.com.tw/dictionary?langpair=en|zh-TW&q=mark&hl=zh-TW&aq=f

symbol       符號；代號；記號

a sign, number, letter, etc. that has a fixed meaning, especially in science, mathematics and music 

http://www.google.com.tw/dictionary?langpair=en|zh-TW&q=symbol&hl=zh-TW&aq=