(Photo credit: http://bit.ly/2ybO602)
I think this picture above very clearly depicts what language is like, though everyone of these delicious lollies are sweet, everyone one of them is slightly different in flavor, shape and most wonderfully of all they all live together in one bowl!
Translating this to understanding English is clear if you are a native speaker. For most people who have spoken English since birth, they understand that though the language is common, there reelly are no two people who speak the same language. Some use more common or informal forms, some use slang, some use formal, some use old fashioned English and so it goes on, but the key point to be seen here is not to be worried about it. All the sweets are sweet and satisfying.
English learners may see it differently. They may easily be convinced early on that English language is set and you just need to learn the vocabulary, the grammar and get opportunities to speak and you will get to be perfect. In fact, this approach may set the learner up for false expectations.
When an ESL learner gets into the pre intermediate levels of English they should be starting to realise that those there are rules, some rules can be broken, and broken again. Then when you are in your intermediate levels, it really is as if everything you learned so far is now going to be thrown out the window! But not all is lost.
If a student has learned their English well, there should be enough flexibility in the understanding to allow their own style or ‘flavour’ to form. This flavor forms when communication, culture, personality and data meet.
There are some speakers whose language is not only indecipherable but also difficult to hear. For me the flavor is harsh and difficult to swallow, but to his neighbor in his community who speaks just like him, it is as clear and as beautiful as a delicious meal at a 5 star hotel!
We all develop different tastes in our life, some can handle spicy food, some need more bland food. Some need the eat the same food every day, some eat from a multitude of cuisines on a daily basis, and our tastes adjust and develop depending on this. So too does our understanding and comprehension of the Englishes out there.
A great course in English taught by an insightful talented teacher can set up an ESL student for a lifetime of interesting diets and flavours. Enjoy!