Aside from “How many languages do you speak?”, the single most terrifying question for any linguist is “What is the easiest language to learn?“
It may indeed be more terrifying, as there is simply no way to answer it simply and the question is in any case largely irrelevant.
Firstly, of course, the question lacks definition. Leaving aside how you define a “language“, we also have to define “learn” (let’s not do that in this post – we’ll just leave it at “reaching the stage of being proficient enough to speak it without recourse to your own or another language”) and “easy“. So what is “easy“?
What I suspect most people are thinking of when they say “easy” in this regard is whether the grammatical and phonological structure is “complex” and, implicitly, whether it is “complex” from the point of view of their own native language.
To be clear, some languages, even objectively, are clearly less “complex” than others from a learner’s point of view, at least initially. Dutch and German are similar and closely related, but it is undeniable that the former (in its current standard form) is markedly less grammatically “complex” than the latter – Dutch makes little use of cases (whereas German has four for all noun phrases), for most purposes Dutch has two genders (as opposed to three in German), Dutch makes minimal use of any subjunctive mood (in German this is restricted but clearly present), and Dutch has two common plural forms (compared to German’s seven). For similar reasons, though the gap is much closer, Spanish is clearly slightly less grammatically “complex” from an objective point of view than the closely related Portuguese or Italian.
However, the questioner’s native language (or indeed any language they happen to know) will have a role. In English we are used to concepts such as word classes (clear distinction between noun, verb and adjective; Malay, for example, can essentially merge verb and adjective), singular and plural (but not dual; Malay generally does not mark plural at all grammatically at all, conversely Lithuanian also has a “dual” form), articles (“the” and “a”; most languages including Russian lack these), and past tense markers (again, Malay lacks these); so English speakers take little account that such things may be considered to add “complexity”. On the other hand, it makes minimal use of grammatical gender (generally only with reference specifically to a man or woman in the singular), case (to the extent that there is even confusion when case is applied for pronouns among native speakers themselves), indefinite plural articles (such as degli spaghetti in Italian or du pain in French), or the subjunctive (very occasionally used, particularly in British English: “it is essential that you be/are there tomorrow”); so languages which do have grammatical gender, noun cases, plural indefinite articles or a subjunctive mood in regular use can appear “complex” – but this is, essentially, not to do with inherent complexity but rather native language bias.
Phonological structure also matters and may be inherent to the question: languages with sounds which are unfamiliar from the point of view of the questioner’s native language will inevitably appear more “complex” (e.g. the range of affricates similar to English ‘sh’ in Russian, or the velar fricative ‘ch’ in German ‘Buch‘/’j’ in Spanish ‘encajar‘); again, the ‘th’ in English ‘the‘ is unfamiliar to speakers of many other languages but is not held to be “complex” by speakers of English itself.
However, the real issue is that grammatical structure is a relatively marginal part of any objective assessment of “easy”.
Vocabulary has to be borne in mind also. Languages which are closely related will generally have a lot of “cognates” – essentially, similar words with similar meanings (even if the parallel is rarely absolutely precise). In this way, learning Dutch provides access to German, Spanish access to Portuguese and Italian, Russian access to Ukrainian and so on. English is of course an oddity, as a West Germanic language with an overlay of North Germanic and, from a vocabulary point of view most obviously, (Norman) French. Therefore a lot of core vocabulary will be shared with German (hier ‘here’), as will some other vocabulary if we know the patterns (vergeben ‘forgive’; also haben ‘have’, verloren ‘forlorn’ making the pattern more apparent); but a lot of more recent vocabulary is shared with French, particular for abstract terms (‘civilisation’, ‘detest’, ‘possible’). Therefore, from a vocabulary point of view, it is sometimes the nominally more “distant” Latin-derived languages which appear initially “easiest” to English speakers.
Common vocabulary is in fact a bigger help than common grammatical structure – grammar can be acquired over time but vocabulary gives a real head start.
Yet, even combined, the pure structure (whether in terms of grammar or vocabulary) is not perhaps the key aspect of what makes a language “easy”…
Perhaps the most important thing which makes a language “easy” is exposure to it.
We learn from that exposure – a system known by linguists as “comprehensible input”. The more opportunity we have for that input – be it YouTube videos, Netflix/Prime audio, online newspapers or whatever – the “easier” the language will become.
It is that simple.
Therefore a language like Spanish, which is in regular use for documentaries, TV series or as a written language online, becomes “easy” because it is easy to find opportunities for exposure to it. Its global role as a mother tongue of half a billion people, a significant European language and indeed as the first language of an eighth of households in the United States only enhances this.
Compare this to even to a fairly prominent, closely related and grammatically/lexically “easy” language such as Dutch and we can see the difference. There is less likely to audio in Dutch on your average TV stream; there are fewer online documentaries or papers; Dutch simply is not as prominent as Spanish globally because far fewer people speak it (either natively or as a second language). Even upon visiting a Dutch-speaking country, exposure is limited by the natives’ undeniably excellent English. Dutch has a marvellous word for ‘easy’ (who cannot like gemakkelijk?) but from an exposure point of view it is quite hard, certainly versus a language like Spanish.
However, at the end of all this, what ultimately makes a language “easy” is our own motivation. Here, we simply need to be honest with ourselves.
How likely are we, really, to put in the motivation to become proficient in a language (as per the above definition) – listening to it every day, reading it frequently, finding ways to practice using it?
That will largely depend on the language, and it does touch on “exposure” above. Will it be easy to get exposure, as per above? Will you want to, pretty much daily, over a period of years?
What makes a good learner?
The better question is: “What makes a good learner?“
I would suggest three things.
Firstly, a willing guesser. You have to be prepared to try; you will get things wrong, but this is how you learn and is, in any case, for the most part irrelevant. If you go to Spain and order a “vino rojo” (literally ‘red wine’, but the Spanish and Portuguese are more inclined to say ‘vino tinto‘ for this) and you get a red wine, you have succeeded – sure, it wasn’t particularly idiomatic, but does anyone care? No. Did it matter? No. Did the waiter appreciate you trying? Yes. Did you get your red wine? Yes.
Secondly, motivation – we have covered that above.
Thirdly, noticing. We will come back to that…