Why/When need some kind of short spelling or pronunciation?

Question

In regular usage, nowadays we use short spellings of words in speaking or writing. For example: - They are in the cinema. => They're in the cinema. - We have been waiting for me. => We've been waiting for me. - etc... I know it makes our vocabulary and understanding easier than the real spelling of words, but my question is: why do we need that type of change and how should it be applied to our regular usage? Most importantly **when should we use this kind of short word when writing or speaking?**

Answer 1

We call those shortened words contractions. In English they are used a lot in casual spoken English. In written English for academic purposes they are best avoided. However, if you are writing conversation like "I've got to go!" Mary yelled, then they must be written like they are said. You will use them in speaking situations and you learn them through practice as you develop more native like speaking ability.