Miss Sandy gave a good answer. Attitude has to do with your emotions and how serious you are about something. Aptitude is your ability. Good question.

Although these words appear similar, their meaning is quite different! Aptitude is an ability that a person is born with. "You have an aptitude for learning languages." "I tried to play the piano, but I have no aptitude for music." Attitude is a state of mind. It is the way a person approaches life, or a particular aspect of life. It is often applied to people in school and work situations. "She came to school with a bad attitude and did no work all day." "He's great to work with because he has such a positive attitude."

There is no need to come up with any complex way of defining the difference between the two because they are only similar in spelling but far different in terms of meaning. Attitude is your settled way of approaching things and it has a lot of nuances that are carried in it. Like if you want to master a language, you need to persevere. That is the kind of attitude that you should have in order to succeed. It is different from having an aptitude for language. Aptitude simply means that you have a knack or leaning towards a particular skill. Therefore, you can say that someone has an aptitude for painting, singing, acting or speaking. Another way to put it is natural talent. Moral of the story: Just because they sound similar they don't have a meaning that is close.