rebecca's pocket

what does "transparency" mean for a language?

I'd be interested to find out by what means they decided relative difficulty of languages. I'd put English much higher than they did, and Russian somewhat lower (I think it's structurally easier than English). My guess would be that they're really talking about "difficulty for a monolingual English speaker" in most cases, but even then I think their rankings are a little screwy.

Transparency seems to be connected to how easy it is to transfer from another language to "this one", how common/related it is.
See for example the notes under French transparency.

Some of the information on the site is wrong or misleading. For example it is not true that Dutch is spoken in South Africa. It was a few hundred years ago, and Dutch was one of the influences on Afrikaans (which is one of 11 official languages of the place).