Should we use different domains for different languages​​?

I have a bilingual website, do I create different domains or subdomains or subdirectories for each language?

Should I use:

• Different areas, eg .com for the English version and a .fr for French language?
• Subdomains as en.scriptol.com for the English language, fr.scriptol.com for French.
• Subdirectories, as scriptol.com/en/ for English, scriptol.com/en/ for French.
• And so on for all other languages ​​...

These three solutions are suitable for different situations.

Subdomains

In this case, the less relevant is the use of subdomains. Indeed, they are seen by search engines such as different sites, then division of the PageRank. Better a site bigger than two small sites.
In fact we should use subdomains only for multiple users, each with access to own Webspace.

Country domains

Using different domains has the same drawbacks but with the advantage of the extension in relation to the language and URL clearer to the public.
The extension on language like .fr for example, gives an advantage for positioning on local search.

Subdirectories

However, having a larger site may outweigh the benefits of geolocation.
If traffic on the site is not large enough to justify multiple domain names, sub-directories are preferable. Using a script to adapt the language to the user is in my experience, effective with the precautions listed in the article.