__If one wanted to make reference to some seemingly simple mathematical / geometrical definitions, which are globally accepted without ambiguities or differences, which books , institutions or web page should be referenced?__

**Let me mention how my question started..... It did with at least 2 controversies that arose among my colleagues and students, and we could not elucidate 100% satisfactorily.**

**1) Does the definition of rhombus include the figures of 4 right angles, then all squares are rhombuses?**

**2) Are the trapezoids or trapeziums, real parallelograms, or are the parallelograms trapezoids or trapeziums? Or are their definitions mutually exclusive?**

**This is not a non-euclidean fat triangles derivative composition, or it is not about if you see a colour light green or light light green; or a smell....it is just about plain definitions of very simple and well known geometric shapes. !?**

**But I am not looking for the definitions now,** __what I'm really looking for is an unquestionable source of these kind of definitions.__

**I have an answer for both of them that I learned at university, but even in social networks I got into troubles with people when I asked these questions and I gave what I thought was a definition that could not be debated.**

**I have more examples, but I think these 2 are enough to explain what happens.**

**Thank you if you have a moment to shed light on my momentary darkness.**
@Adrián

maths.professor.am

Checkout Wolfram Alpha. Wolfram Alpha says squares are rhombuses. Didn't bother entering the other ones. I'll drop a link:

https://www.wolframalpha.com/input/?i=are+all+squares+rhombuses