Google Analytics

2 domains; same code

[fashezee]

We often use sub-domains or the TLD to publish websites in their language countries language.

Ie.
domain.com = English
domain.ca = French

Must we use different codes for each site or can we use the same for both?

[Quadrille]

Each domain or subdomain is unique, and Google respects that; if you want useful results, you need to treat them that way too.