The Oxford English dictionary defines idioms as a group of words with a meaning of its own. These are phrases, which meaning has already been institutionalized.

It is important for students who are learning English as a second language (ESL) to attempt to substitute literal phrases with idioms because it will help foster rote-learning and analytical skills in both written and spoken English.

In delivering a course on idiomatic expressions, instructors have to be mindful of the following:

1. Instructors have to make sure that their students understand that idioms are invariable and the words in the phrases cannot be substituted. For instance, “beating around the bush,” which means equivocation, cannot be phrased as “beating around the tree.”
2. Before asking students to incorporate the use of idioms in written or spoken English, instructors have to make sure they relay the stand-alone meaning of each expression. For instance, before asking them to use “raining cats and dogs” to say “Oh no! It’s raining cats and dogs today” first explain that it is commonly understood that cats and dogs are two species that do not get along by nature. It is natural for people to witness a cat and a dog engage in a fight. Hence, we can equate heavy downpour with a fight.
3. In light of this advice, instructors should not overwhelm their students by introducing too many idiomatic expressions. Ideally, only two idioms per day should be introduced. Remember that idioms are institutionalized expressions that are bound in Western culture and context. These metaphorical phrases may not hold the same meaning for non-westerners. The most effective way for instructors to teach idioms is to help their students visualize it. For advanced learners, a clear explanation of how the expression came to be or they were institutionalized will suffice. For beginners, instructors can make use of pictures and games.

Though learning to use idioms is difficult, it is not impossible for ESL students. Instructors simply have to be mindful of the following:

1. They should not assume that their students will interpret the metaphorical expressions the same way Westerners would. For instance, the idiomatic expression “keep your fingers crossed” can easily be interpreted by a native speaker as hope for the best. However, it may not be as easily decoded by an ESL student, who in tough times would think of offering a prayer, more than crossing his fingers.
   
   
2. The most dangerous pitfall in delivering a course on idiomatic use is for the instructor to present it right after teaching syntax. Instructors have to remember that idioms do not follow any grammatical arrangement and are in fact abnormally constructed in the sense that there are no patterned relations or rules that govern their use. It is best to introduce idioms after the students have a working grasp of the rules and structure of grammatical English. This way, the instructor will be able to avoid confusion on how words are ordered in the English language.