1. Regardless of the fact that; even though: Although the room is big, it won't hold all that furniture.
2. But; however: He says he has a dog, although I've never seen it.
Usage Note: As conjunctions, although and though are generally interchangeable: Although (or though) she smiled, she was angry. Although usually occurs at the beginning of its clause (as in the preceding example), whereas though may occur elsewhere and is the more common term when used to link words or phrases, as in wiser though poorer. In certain constructions, however, only though is acceptable. When though introduces only a part of a clause rather than a whole clause, although is not possible: Most people in attendance applauded loudly after the performance, though (not although) not everyone. Another construction that requires though is the following: Fond though (not although) I am of sports, I'd rather not sit through another basketball game.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendicies
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.