Idiomatic expressions-- English is full of idiomatic expressions; in fact, many non-native speakers say that that's the hardest part of English to learn. These expressions are so common that we often don't realize we're using them. It's fairly easy to look at our writing and edit out idioms based on, for example, American football, so that we might choose NOT to say "It's time to drop back and punt" or refer to critiquing a decision as "Monday morning quarter-backing." What's harder to spot are those idiomatic expressions that are built into the language. One very difficult group of expressions is the set of verbs known as "phrasal" or "two-word" verbs. Think for a minute about this set of verbs: pull up, pull over, pull out, pull on, and pull in. The many meanings of those expressions cannot be arrived at by looking up the verb "pull" in the dictionary, and each of the prepositions. The meanings are idiomatic; that is, they are not contained in the simple definitions of the words. Because of this, these phrasal verbs are not easily learned or understood by non-native speakers of English.
One very dramatic example of this occurred in airplane accident. The pilot and co-pilot were both non-native speakers of English. After the plane crashed into a mountainside, investigators retrieved the "black box." The last words recorded in the cockpit were "What does 'pull up' mean?" The standard usage for air traffic controllers and pilots is "Climb, climb." In this case, however, either the air traffic controller, in panic, forgot and used the idiom, or (and I think this is more likely) the warning system built into the plane (probably American made) used the expression "pull up." I believe this because I have heard that phrase coming from the warning system in documentaries about crashes. This prompted me to do some research on these phrasal verbs. I tested students who had come to the U.S. to student in an International MBA program. These students had very high scores on the Test of English as a Foreign Language -- their English was very advanced. Yet they only averaged 14 out of 27 correct answers on a test of everyday phrasal verbs, such as put on, look out, turn in, etc. Tests of intermediate students in other countries showed even worse results -- 7 out of 27 on average. These verbs are often the last aspect of English acquired by learners. Considering that many of them also have different meanings in British vs. American English, and that many of your readers around the world will have studied British English, and you can see why use of phrasal verbs can cause major problems!
