Why linguistics is useful when learning a foreign language

Betsy Lowe has been keeping me up to date on her endeavor to learn Hungarian, and the frustrations that go along with any attempt to learn a foreign language. She commented specifically on exceptions in vowel harmony, to which I replied:

"After a while those irregularites will start to resolve into patterns. For instance, my dad, who got his degree in linguistics, was at first puzzled by the Arabic definite article, which is usually al-, but the -l- changes to the first letter of the noun it attaches to in some cases. After a while he figured out that the -l- stays an -l- only when the first letter of the noun isn't a coronal consonant, and once he realized that he no longer had to memorize the cases; it was easy to figure them out."

As another example, in many languages velar stops become post-alveolar stops or alveolar fricatives before front vowels. Thus in Italian syllables originally beginning with /k/ now begin with tʃ, e.g., cibo, 'food' is pronounced tʃibo. In Italian the pattern is not difficult to remember even if you don't know any linguistics: c is k before a, o, and u, and tʃ before i and e. However, a little linguistics knowledge makes it even simpler: tʃ before front vowels, k elsewhere. Such knowledge is especially helpful in situations like the Arabic case, where without linguistic knowledge the learner merely has to memorize a long list of letters that take the article al- and another long list that take aC-, where C represents the first letter of the noun the article precedes.