basic form not marked for finiteness (like participles). In the third stage functional morphology starts to appear, with the flection of nouns and verbs Language difficulty and learning time The time taken to reach a high level of proficiency can vary depending on the language learned. In the case of native English speakers, some estimates were provided by the Foreign Service Institute (FSI) of the U.S. Department of State — which compiled approximate learning expectations for several languages for their professional staff (native English speakers who generally already know other languages). Category I Languages include e.g. Italian and Swedish (24 weeks or 600 class hours) and French (30 weeks or 750 class hours). Category II Languages include German, Haitian Creole, Indonesian, Malay, and Swahili (approx. 36 weeks or 900 class hours). Category III Languages include a lot of languages like Finnish, Polish, Russian, Tagalog, Vietnamese, and many others (approx. 44 weeks, 1100 class hours). Of the 63 languages analyzed, the five most difficult languages to reach proficiency in speaking and reading, requiring 88 weeks (2200 class hours, Category IV Languages), are Arabic, Cantonese, Mandarin, Japanese, and Korean. The Foreign Service Institute and the National Virtual Translation Center both note that Japanese is typically more difficult to learn than other languages in this group. There are other rankings of language difficulty as the one by The British Foreign Office Diplomatic Service Language Centre which lists the difficult languages in Class I (Cantonese, Japanese, Korean, Mandarin); the easier languages are in Class V (e.g. Afrikaans, Bislama, Catalan, French, Spanish, Swedish). The bottleneck hypothesis The bottleneck hypothesis strives to identify components of grammar that are easier or more difficult to acquire than others. It argues that functional morphology is the bottleneck of language acquisition, meaning that it is more difficult than other linguistic domains such as syntax, semantics, and phonology because it combines syntactic, semantic, and phonological features that affect the meaning of a sentence. For example, knowledge of the formation of the past tense in English requires both phonological patterns such as allomorphs at the end of the verb and irregular verb forms. Article acquisition is also difficult for L1 speakers of languages without articles, such as Korean and Russian. One study compared learner judgments of a syntactic feature, V2, and a morphological property, subject-verb agreement, using an acceptability judgment task. Researchers found that while Norwegian speakers who are intermediate and advanced