Obtain means 1.Come into possession of "How did you obtain the visa?" 2.Receive a specified treatment (abstract) 3.Be valid, applicable, or true While attain means 1.To gain with effort 2.Reach a point in time, or a certain state or level 3.Find unexpectedly 4.Reach a destination, either real or abstract cowboy...

The main difference is that some mean to get actual things, and others mean to achieve something or reach a goal. To obtain or acquire means to get or buy a physical object (car, house, shoes, MP3 player, etc.). To attain or gain means to get something that is not physical (power, influence, a job, a title, someone's love, etc.).

Reading the rest of your question, I see some that have not yet been answered. Obtain and acquire are synonyms. Attain and gain are sometimes synonyms. Cowboy gives a very good distinction between obtain and attain. Sometimes gain is used in a manner that differs from the others. It can also mean to obtain something additional. For instance, when we get heavier, we say "I've gained weight."

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