What are the realistic/optimal (or maximal) number of words of vocabulary that can be learned (retained and later successfully accessed) by an adult learner of a foreign/second language? (Unit: per day, week, or year.)

Initial research:

  1. Read the Wikipedia article - result: Only focuses on children and their native language acquisition (as many articles do) vs. adults, who train conscientiously!

  2. Google search: Which search terms would you recommend? Results from "vocabulary acquisition" and "amount of words/vocabulary" (+daily) are in review. I did not find much yet, see below..

  3. Google Scholar: In progress... ("vocabulary acquisition" and "adult vocabulary acquisition speed")

Unverified statements found from Google search:

"I am a student at the Defense Language Institute. We are required to learn about 80 words a day." (Source) - I tried to access the DLI / DLIFLC website to verify this, but the website was down yesterday (31.08.2012, 1:30 am, GMT+9)

  • 2
    $\begingroup$ What initial research have you already done? Since you are looking at foreign languages, it will depend heavily on how far the language you are learning is from your native tongue. I.e. I can learn Italian easier than I can learn Mandarin. $\endgroup$ Aug 31, 2012 at 14:31
  • $\begingroup$ My question was not about how long it takes to learn a language, but regardless of the goal (which could be a B1 or a C2 in the CEFR) how . So my question does not depend on the language, in my opinion. As I didn't ask about how many complex grammar patterns I can remember, but just about words / vocabulary. The difficulty of certain can (only) be "ironed out" by spaced repetition of those words and modern tools like "Quizlet" are extremely good in determining which words are difficult for me, thus prioritizing those. So this ain't my problem. $\endgroup$ Sep 1, 2012 at 8:18
  • $\begingroup$ I will post my "initial research" results here ASAP, no worries. But I just didn't find anything reliable yet... My initial research included that I checked the SE network and this site for similar questions and I couldn't find one yet. Thus I think think that anyone contributing sources will help further the answer to this question. $\endgroup$ Sep 1, 2012 at 8:20

2 Answers 2


Try keywords like: "second language learning number of words per"

Some suggest 3-6 words per hour of reading, which is afterwards used for calculation of average per week, month, year. References of studies to support this claim are missing though: http://ip-173-201-189-182.ip.secureserver.net/archives/sla/waring120304.pdf

Several times I found references on this study: Miltion and Meara (1995).

A longitudinal study by Milton and Meara (1995) found that adult learners of English as a second language could learn 2650 base words per year. more at: http://iteslj.org/Articles/Cervatiuc-VocabularyAcquisition.html

I remember it should be 7 words a day. If it is not, it should be at least divided into blocks of this size. If you google this number, it is mentioned on several sites, I do not remember the book I got it from.

I would be careful using these numbers, it is likely that they depend on the techniques that students and teachers tend to use.

  • $\begingroup$ Dear Oriesok, thank you for your very useful answer! I share my careful assessment with you. What to do though? Discovering more research and narrowing down the wildly fluctuating numbers (cp. 6-12(2hx3-6) words/day to 48-80 words a day at DLI below!) to a clearer estimate. $\endgroup$ Sep 6, 2012 at 6:08
  • $\begingroup$ The first link no longer works; is it the same as this one: sealang.net/archives/sla/waring120304.pdf? $\endgroup$
    – Tsundoku
    Dec 29, 2016 at 12:38

I am an instructor at DLI... if you just took our unit vocab lists for the 63-week Arabic basic course, there are over 11,000 words listed. The vast majority are discarded well before students ever take the DLAB (Defense Language Aptitude Battery) test. In order to achieve a 2/2 (Reading, Listening) on the test, a student could be expected to have passive contextual access to at least 3,000 vocab words.

  • $\begingroup$ Dear Mike, thank you very much for your interesting answer! It's not entirely clear to me though, do you mean that the actual words learned per 63 weeks have to be 3.000? I mean, based on my source above, he said 80 words / day, while 3.000 / 63 = ~ 48 words. So you do not have a plan or benchmark in terms of minimum daily words or do you? Or does it depend on the language? $\endgroup$ Sep 4, 2012 at 15:21
  • $\begingroup$ Since the DLI website worked again (for me), I tried to find this exact information on your institutions website, but as there is so much information and this "key figure" is probably not seen as of interest to the public, I couldn't find it in the time I was going through it. So that is why I'd be quite interested in manual verification, ideally with a public source included, if you guys are allowed to share material where such a number is mentioned. $\endgroup$ Sep 4, 2012 at 15:23

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