Grammar is not a mere shibboleth of rules, but there is also a reason behind the rules, diachronically or synchronically. Syntax provides underlying reasons for the rules in grammar so by having sufficient syntactic knowledge (and awareness), teachers are able to explain it to students or take it into consideration in teaching practice. It will also enable teachers to comprehend the relation between grammatical elements (Wilkins, 1975), e.g., tenses and aspects, and how they interact in linguistic structure. Simply as an understanding for the teacher, this is very useful. They will be able to learn new grammatical materials and know the reasons behind them, design grammar materials accordingly, and are prepared to answer critical questions from the students.
