Yan is an eight-year-old boy born in New York to Chinese parents who speaks Mandarin and Chinese at home. He lived in China for one year and attended preschool there. Mandarin has characteristics like not distinguishing parts of speech or expressing verb tenses and plurals in the same way as English. Yan makes errors with articles, plurals, verb tense and phonemes because those concepts are expressed differently or don't exist in Mandarin compared to English.