Adding references for glossaries I am writing my thesis and I have decided to add a list of glossaries to explain certain terms. I decided to copy most definitions for these terms from here because I believe they are best explained there. This site, SEVOCAB provides definitions by the IEEE for international standards in Software and systems engineering. 

My questions:

1) Am I correct in copying directly the definitions from here? I thought it would be best to do so because you are using approved definitions to explain concepts that may frequently be interpreted differently by different authors

2) Of course I understand that I need to cite the website and that the definitions come from there. I thought of adding a sort of disclaimer or reference either at the beginning of the glossaries or somewhere in the thesis itself. For example, I have a section called clarification of terms whereby I make a distinction between Software Engineering and Software Development. How should I go about this?
1) If the definition is well-known and everyone uses it in the same way, you don't need a definition. If you use it in a certain way that might differ from others and thus needs to be defined, you should do so in the thesis itself, when the term first appears. Otherwise a reader might come to the wrong conclusions and only later realize that you meant something different by this term. Jumping back and forth to the definitions every time is also not that nice...
So I would suggest that you define the terms where you need them, where they appear in the work, and then add an index of symbols, only stating at which page each term gets defined (and maybe a one-line "name" of it) and no further definition in the index.

2) As you define the terms yourself, just like you need them, it won't be necessary anymore to use the homepage.
However, if you want to take definitions from there, you should say so. If you copy many definitions, you might want to say so at the beginning of the thesis or at the beginning of the chapter where the definitions appear.