You're learning English, right? You might think you can work out the grammar and have built a vast vocabulary, but then you come across an expression like "plos". 

According to online urban slangdictionaries, it means "parents looking over shoulder". Teenagers are to blame. They have their owncode, including "text speak" when they are on the internet or using their phones.

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Text speak has a lot to do with inventing cool new terms — and these change quickly. Maybe you shouldn't be surprised if an English friend says you sound a bit old-fashioned. 

The modal verb "shall" is on the way out because "will" sounds more natural these days. Bas Aarts, Professor of Englishlinguistics at University College London says, "If you have two words which more or less express the same meaning, one of the two words will get pushed out of the language."

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People have been shying away from using the modal "must" because it sounds authoritarianand people are choosing to express obligation in different ways. It sounds nicer to soften obligation by saying "might". For example, "You might like to read this article."

Progressive tenses — formed from the verb "be" and the suffix "ing" — are used for ongoing situations, for example, "I'm writing this article for you to read". But its use has been increasing rapidly. Bas Aarts says that this might have to do with advertising. 

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A fast-food chain uses the expression "I'm loving it" in English-speaking countries. But the verb "love" expresses a state of being — as opposed to doing — and is usually used in the simple form, for example, "I love it". These days, people are usingstative verbs in the progressive more and more.

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Before you despair and throw your English book in the bin, be assured that some words take a very long time to change. 

According to Professor Mark Pagel at Reading University in the UK, pronouns like "I", "you" and "we" evolve slowly — a thousand years ago we would be using similar or sometimes identical sounds. 

Nouns and adjectives, on the other hand, get replaced rapidly — and in 500 years or so we'll probably be using different words to the ones we have now. But let's leave the problem for the future generations.