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 slang dictionaries, it means 'parents looking over shoulder'. Teenagers are to blame. They have their own code, including 'text speak' when they are on the internet or using their phones.

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 English linguistics 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."

People have been shying away from using the modal 'must' because it sounds authoritarian and 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. 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 using stative verbs in the progressive more and more.

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.
词汇表
grammar 语法
vocabulary 词汇
urban slang 现代俚语
code 代码，语言，代号
cool 酷的，时尚的
term 表达，术语
old-fashioned 过时的，老派的
modal verb 情态动词
on the way out 即将过时，即将被淘汰
linguistics 语言学
shy away from 回避，躲避
authoritarian 专制的
obligation 义务，职责
progressive tenses 进行时态
suffix 后缀，词尾
advertising 广告业
stative verb 静态动词
pronoun 代词
noun 名词
adjective 形容词