1
$\begingroup$

Possible Duplicate:
Why is closure omitted in some group definitions?

I have just started studying about groups, so pardon me if this is a lame question

while i was reading the definition. the author states that

'strictly speaking the closure law is not necessary since a binary operation on a set necessarily satisfies it'

can anyone elaborate on this statement?i am not sure i quite understand it

1 Answers 1

3

He just means that the definition of a binary operation includes closure, so it is not strictly necessary to include it again in the definition of a group.