The Importance of Understanding American English Phrases
There are two sides to every coin, such is the case in the difference between formal and authentic English. It is necessary to know the technical aspect of English because it is foundational. By the same token, it is necessary to understand the language as it is actually spoken in society.
In American culture, many idioms, verbal phrases, slang, etc. are used in daily conversation as the norm. Therefore to not understand this aspect of the language places a translator or interpreter at a severe disadvantage in rendering an accurate understanding of what was communicated.
Judging whether the language used is correct grammar is not the issue, the goal is knowing what was communicated and giving a correct rendering of it. In my experience in working with ESL students, they have no idea what is being communicated when phrases are used. With knowing only formal English, native speakers can understand what they communicated, however, the ESL student may be at a loss of what was communicated by a native speaker when phrases are used in a statement. At best, it is simply ignored, at worst it can be detrimental.
It is my personal opinion that more time and effort should be spent on learning phrases from newspapers, magazines, radio, TV etc. When a phrase is spoken, write it down and google it to determine it's meaning. Ask a native speaker about it and the context it's used in.
I'm sure with an inclusion of this aspect of learning our competancy will be greatly improved.