Whatever obstacle is correct and means any obstacle, any at all. Whichever obstacle is also correct but the meaning is different - any of the already mentioned obstacles.
The American Heritage Dictionary seems to allow both: Both whatever and what ever may be used in sentences such as Whatever (or What ever) made her say that? Critics have occasionally objected to the one-word form, but many respected writers have used it. The same is true of the forms whoever, whenever, wherever, and however.
"Whatever" in its traditional sense, such as in "whatever you might think," or "whatever choice you make," is a totally different animal than this kind of teenage use that has spread everywhere and indicates a total dismissal of the line of discussion or the person.
If you go into a public library, you can borrow whatever you want - any book, or any of the videos or CDs if they have them. If you're given a choice of a dozen books, you can borrow whichever you like of that given group. Both words are correct there, but 'whichever' has more of a definite group in mind, whereas 'whatever' is more open.
No. Whenever is convenient = At whatever time suits you Whenever it is convenient = At whatever time meeting up is convenient
Which sentence is right? I don´t mind, do whatever you want. I don´t mind, do whatever you want to. I don´t mind, do whatever you wanto to do. There are many sentences in which I don´t know if I should use "to" after "want". And here: I have to go to school but I don´t want I have to go to...