Hello, Ruby goes long way from born 21 year ago to what is nowadays. As a multi-paradign language allows programmers to code from imperative to functional style. This gives Ruby to be modern and wide used language in these days. Ruby is built on idea to be as fun, understandable and focused programming language for people. But i think it carry "complicated behaviour" in some method naming. In this documentation is written: (http://docs.ruby-lang.org/en/trunk/syntax/methods_rdoc.html) > The bang methods (! at the end of method name) are called and executed just like any other method. However, by convention, a method with an exclamation point or bang is considered dangerous. In ruby core library the dangerous method implies that when a **method ends with a bang (!), it indicates that unlike its non-bang equivalent, permanently modifies its receiver**. **Almost always**, ruby core library will have a non-bang counterpart (method name which does NOT end with !) of every bang method (method name which does end with !) that does not modify the receiver. This convention is typically true for ruby core library but may or may not hold true for other ruby libraries. Hightlited part of citation talks about that method with exclamation mark modifies its it receiver. What is good incredible because i could choose between imperative habit and modify receiver, receiver (object) when i need to, but i can also create new data data, and code in functional habit. Eg: i can create new array with **map** method, but always i can modify existed object with **map!**. What is incredible and easy to understand. Or i want to get unique values from array by **uniq** assign into new variable. Still it is able to modify origin array with **uniq!** Second highlighted part is about confused part. It tells to programmer be careful. on the lookout. Not all methods follows this great design. In Ruby are methods which are "inconsistent" inconsistent in naming. Eg. Many built-in Array methods modify like * clear * concat * delete * delete_at * delete_if * fill * insert * keep_if * pop * push * replace * shift * unshift are dangerous because and modify its receiver. What is confusing confused for many programmers and it brings unexceptional behaviour without study of documentation deeper. more deep. I think Ruby is popular for people because it communicate with programmer like in human language. Nowadays are getting functional programming and languages high popularity and trend increase more and more. It could be great to remove that one word ("Almost") and have Ruby as language more clear, unambiguous and brings more functional principles into language what we like and love.