theorem vs. lemma: What the difference between lemma to theorem​?

[shahar]

What the difference between lemma to theorem​?

 

[JeffM]

They are both propositions that have been proved. The difference is in the perceived scope of the proved proposition. A theorem is considered to have some significance beyond itself. A lemma is significant only in that it is used to prove a theorem.

In other words, the distinction between a theorem and a lemma is a subjective judgment on the value of the proposition proved.