If something is "common" this means that many people can relate to it or have it. If something is "ordinary" this means that it is plain or not special. For instance, in the sentence "Cancer is a common disease", I am not saying that cancer is ordinary. Cancer is in fact, a horribly extraordinary disease. I am saying that many people have cancer. But, in the sentence, "A green shirt is an ordinary outfit". I am not saying that many people have green shirts. I'm saying that a green shirt is nothing special. I would say a common SIM card if you mean that many people have the same SIM card. And, I think that this is what you mean. I would not say, an ordinary SIM card. As, the SIM card could very well be exceedingly hi-tech and not ordinary at all. Your editor should not have changed your sentence. Explain this to him. Here are two definitions for "common" and two for "ordinary" to help you understand further: COMMON: 1.belonging equally to, or shared alike by, two or more or all in question: common property; common interests. 2..widespread; general; ordinary: common knowledge. 5.of frequent occurrence; usual; familiar: a common event; a common mistake. ORDINARY: 1. of no special quality or interest; commonplace; unexceptional: One novel is brilliant, the other is decidedly ordinary; an ordinary person. 2. plain or undistinguished: ordinary clothes.

both common and ordinary = average However is you describe people as 'common' it implies that they are vulgar and without any manners.

Good question! The word "ordinary" came into English from French which ultimately came from Latin and has a meaning of something like "usual"; "common" is from Middle or Old English and has a meaning of low or among poor people. English is not one language but a mix of several which gives it a rich vocabulary that lets you pick and choose exactly what you want to express. My Skype: brian.madden4