In the long run, having a language with words of diverse etymologies makes a language harder to learn, cf. English.
That's an empirical claim. Is there any evidence to back that up? In particular, is there any standardized way to characterize which languages have more diverse etymologies and which have less? Is there a standardized way to compare the difficulty of learning languages as a second language in the abstract (as contrasted with the difficulty of learning some particular language given a particular first-language background)?
I get the distinct impression, from my acquaintance with people from all over the world, that many second-language learners think learning English is rather easy, not least because there are so very many opportunities to be exposed to English and to practice English all over the world.
Yes, Yes, and Yes. Languages and the relationships between them has received a lot of attention / study. Grated not all linguistic family's have received the same attention but there are thousands of reasonably distinct languages most of which have been reasonably well documented.
PS: Learning the language is not just about learning _ as a second language, primary schools spend a lot of time teaching the proper way to communicate. And English requires far more instruction time than some other closely related languages like Spanish.
That's an empirical claim. Is there any evidence to back that up? In particular, is there any standardized way to characterize which languages have more diverse etymologies and which have less? Is there a standardized way to compare the difficulty of learning languages as a second language in the abstract (as contrasted with the difficulty of learning some particular language given a particular first-language background)?
I get the distinct impression, from my acquaintance with people from all over the world, that many second-language learners think learning English is rather easy, not least because there are so very many opportunities to be exposed to English and to practice English all over the world.