Stack Overflow
Q&A for professional and enthusiast programmers
Super User
Q&A for computer enthusiasts and power users
Unix & Linux
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Quantitative Finance
Q&A for finance professionals and academics
MathOverflow
Q&A for professional mathematicians
Lifehacks
Q&A for people looking to bypass life's everyday problems with simple tricks
German Language
Q&A for speakers of German wanting to discuss the finer points of the language and translation
English Language & Usage
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Computer Science
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Mathematics
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Data Science
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Cross Validated
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization
Code Golf
Q&A for programming puzzle enthusiasts and code golfers
Code Review
Q&A for peer programmer code reviews
Ask Ubuntu
Q&A for Ubuntu users and developers
Software Engineering
Q&A for professionals, academics, and students working within the systems development life cycle
Server Fault
Q&A for system and network administrators