Even parts of speech are different, as you can see. As in English, verbs change to show tense, but so do adjectives, because Japanese is an inflected language. It is cold. It was cold. But one of the greatest differences has to do with levels of politeness.
People speak differently depending on the person they are talking to, or talking about.
A high-school student uses different forms to speak to the class teacher than when speaking to classmates, and the forms used by boy and girl students are slightly different, too. A person will use a different word for father, for example, when speaking to him and when speaking about him to someone else. These changes reflect the relationship between people, and their relative social positions. This is an important way in which the language influences how people think about each other. Of course, Japanese children learn all these things we consider difficult naturally, as we learn the many difficult aspects of English.