What is an example of proto-indo-European?

Proto-Indo-European is the linguistic reconstruction of the common ancestor of the Indo-European languages. There is no written record of this language, so the knowledge of it that we have has been reconstructed using historical linguistics.

Some examples of reconstructed Words are the numbers one through ten:

1. one = Hoi-no-/Hoi-wo-/Hoi-k(ʷ)o-; sem-
   
2. two = d(u)wo-
   
3. three = trei- (full grade), tri- (zero grade)
   
4. four = kʷetwor- (o-grade), kʷetur- (zero grade)
   
5. five = penkʷe
   
6. six = s(w)eḱs
   
7. seven = septm̥
   
8. eight = oḱtō, oḱtou or h₃eḱtō, h₃eḱtou
   
9. nine = (h₁)newn̥
   
10. ten = deḱm̥(t)