You "get off" the bus. You can also "get down from" the bus which is a synonym in this context but is less commonly used. If a horrible insect lands on me, I might tell it to "get off!" If a dog is jumping up at me, I might tell it to "get down". I know animals can't understand English but I am not mad!

"To get off" also applies to buses, planes, trains, motorcycles, bikes, etc. For instance, "I got off the bus / train / plane / motorcycle / bike." You don't say it for taxis, boats or hot air balloons though. You say "I got out of the taxi / boat / hot air balloon." You can say it for cruise ships though. For instance, "We got off the cruise ship and explored what Hawaii had to offer." The type of boats I am speaking about are the small boats that families own and take out on the river, etc. For these types of small boats, I think it is more common to say "to get out of the boat." The verb "to get out of" applies to canoes as well. One gets off of a jet ski though. If someone is standing on a surface, then you also say "to get off". For instance, "Get off of the table.", "Get off of the deck.", "Get off box.", etc. I guess we are emphasizing that they are ON a surface. Technically, you can also say "Get down from the table" though since the person will be at a level higher than where you are standing on the floor. Sorry if this complicates things for you. It is a little difficult to explain. :)

1. ''Off'' is the opposite of 'on'. So, for example: .. if a child is standing on the table, his mother would say 'Get off the table'. .. if you are travelling on a bus and you reach your destination, you get off the bus. ...if you are on the phone and someone urgently needs to make a call, you get off the phone. 'Get on' and 'Get off' are most frequently used for public transport - bus, plane, train and so on. 2. 'Down' is the opposite of 'up'. If someone is high up somewhere ( in a tree, on a ladder) they need to 'get down' in order to return to ground level. The kitten climbed to the top of the tree, but then it couldn't get down again. It was difficult to get down the stairs carrying my heavy suitcase. Yes, you are right, both of these expressions translate as 'descendre' in French. But if you concentrate on the on/off and up/down contrast, you'll hopefully see the difference. One key difference between French and English is the way that English relies heavily on combinations of simple verbs (like 'go' or 'get' or 'come') in combination with prepositions and adverbs. For example, 'entrer' and 'sortir' can be translated as 'go in' and 'go out'. As you can see, it is these prepositions and adverbs which carry the meaning.

In American English, a lot of times you say "get down" to someone if they are above you. For instance, if they climbed up a tree, you might yell up to them "Get down here now!" This means that they need to come down onto the ground where you are. The same holds for people who are on a floor higher than yours. So you might yell up the stairs to them "Get down here now!" This means that they need to come down to the floor that you are on. This could also apply to a child that is in a bunk bed. They are still higher than your eye level, so you can yell "Get down here now!" to mean to get out of the bed and to stand on the floor where you are. If a dog has his front paws on a kitchen counter, you can also yell "GET DOWN (from there)!" Like Michael said, you can yell "Get off (of me)!" if an insect lands on you or if a dog jumps up on your lap, etc. You can also say "get these clothes off of me." In this case, you are asking the person to help you undress / to take the clothing OFF of your body. :)