In learning language especially English, grammar is one important thing to be considered. According to Greenbaum and Nelson (2002: 1), the basic part of language is grammar. By learning grammar, the students can easily to learn and understand about language. So, they will understand it, if they know well about grammar.
Unfortunately grammar is often considered difficult. One of the English grammar that is problematic for ESL students is conditional sentence. Many students have difficulty remembering the patterns of if-clauses. This present study would like to investigate the common errors made by the students in constructing if-clauses.
Such kind of difficulty may be as a result of many factors such as limited knowledge of the students or L1 interference (Ellis, 1997: 19). This study would like to identify what types of errors (e.g., omission, addition, etc) made by the students. The results of the study would be useful information to formulate a teaching strategy/-ies a teacher should employ in teaching if-clauses to ESL learning.
According to Swan (2005: 233) if-clause is used to express a condition or supposition. There are some patterns that can be used to convey different implications with certain situation. An example of if-clause is this if-clause is used to give suggestion. Suggestion has politer sense than instruction, because the second speaker is the one to decide whether or not she/ he will do the suggested action. The pattern of this sentence construction is if-clause + should/can. And the example of this rule is “If you want to be a singer, you should practice singing well”.