grammaticalityprepositionsword-choice
Is it better to write "on the side" or "at the side"? I always thought that "on the side" was the correct form, but today I've seen the sentence:
The thorax is protected by the ribs at the sides.
And, in the same book,
The cheeks are on both sides of the face.
The only thing wrong with your assumption is that anyone but a non-native speaker would say "by the bus." As the others have pointed out, the construction would be "by bus" or "by train" or whatever.
Nevertheless, it is certainly possible to say
John went to the academic conference on the bus.
Here is a movie poster that illustrates what I'm talking about:
Some may object that this might seem ambiguous, that it might seem as if the conference were being held on the bus itself, but in normal informal speech it would be easily understood. More likely the sentence would be reordered in this case, such as
John went on the bus to the academic conference.
The construction might be easier to understand as a statement rather than as a question. We would have thought otherwise, if the economy had been in better shape is a sentence on the pattern sometimes taught to foreign learners as the third conditional. It describes something that didn’t happen, and is formed by would (or some other modal verb) + have + past participle in the main clause, and if + past perfect in the ‘if’ clause.
When a sentence containing a modal verb (would in this case) becomes a question beginning with one of the wh- words (why in this case), the subject and the modal verb are inverted. That is how we end up with Why would we have thought otherwise?
Best Answer
When I see questions like this, I like to point out that this on-or-at dilemma plays out in other ways, not just with the word side. Both prepositions have a host of meanings, some overlapping, some not. Context is everything!
Sometimes swapping the preposition will cause a sharp change of meaning:
(In those examples, on means "atop", while at means "nearby".)
Other times, they can't be swapped; one preposition fits very naturally, while the other creates a seemingly nonsensical expression:
Then there are idiomatic uses, where one preposition is more fitting than the other:
But sometimes, the difference between the two is minimal, because one of the several meanings of at (and on) is "in a particular place" (which is why you were having problems with the word "side"):
Which is better in those situations (such as Carter's excellent side of the road examples)? In those cases, it may just boil down to a matter of personal preference. Then again, there could be a clear-cut favorite, depending on the context:
Here, either on or at could be used, if the sentence is merely saying that she was physically located near her brother's left arm. If the sentence is meant to suggest emotional support, though, then that would be better conveyed with the idiom at his side. However, if there was a feud in progress, and the brother and sister were allies, then on his side would be the best way to express that.
Lastly, you would always use "on the side" is when alluding to a side dish: