If something happens several times in a row, it happens in exactly the same way each time and nothing different happens in the time between.
Example:"He won two gold medals in a row."
"At a stretch"means to do something without stopping.
Example:"He used to read for hours at a stretch."
So as you see, they don't mean the same thing.
On the other hand,"to do something for two hours straight.", means that you do something continuously, without interruption,so it has the same meaning with "at a stretch."
Example:"They have been studying for ten hours straight.", or "They have been studying for ten staight hours."
Ditto Joe. Let me add:
To "enlighten" is to give information or wisdom. To "inspire" is to motivate.
"Enlighten" is rarely used today. But an example of a correct usage is, "I didn't know about the new rules until my boss enlightened me."
Perhaps somewhat more common is the adjective "enlightened", meaning "wise" or "compassionate". Like, "Tsar Alexander considered himself an enlightened monarch."
An example sentence with "inspire" is, "I was inspired to buy a new car by the desire to impress my girlfriend."
They're not really the same thing at all. I could get new information and do absolutely nothing about it, I might just say, "yeah, whatever". I could be inspired without getting any new information. Perhaps someone just encouraged me.
Where they might somewhat overlap is that "inspire" can be used to mean that one idea led to another. Like, "Mr Smith's latest novel was inspired by a story he read in the news." He got some idea or information, and that idea led to another idea.
But I can't think of any sentence where you could substitute "inspire" for "enlighten" or vice versa without significantly changing the meaning.
Best Answer
An opinion is something that is a personal belief, and perhaps not universally accepted. A good example of this would be the Opinion column of a newspaper, where the editor discusses a position on an issue with more emotion and personal perspective than the rest of the fact-checked and neutral paper. By marking this column as "Opinion", the editor makes it distinct from the News, and the reader is expected to understand that the Editor is speaking only for themselves.
Since an opinion does not need to have the weight of evidence behind it, it is also used as a way to dismiss someone's position: https://www.youtube.com/watch?v=pWdd6_ZxX8c
A concept means an idea, and comes from the same word as "conception", meaning the point at which something new is created.
One example might be "concept" cars, exotic and elaborate vehicle designs that are never intended for mass production, but exist as showcases for art and engineering. http://en.wikipedia.org/wiki/Concept_car