There are many suffixes to learn.  Two suffixes which are easily confusing are –able and –ible because they sound alike. 

A/an and the are known as articles.  A and an are indefinite articles; the is a definite article. 

A and an are used only with and in front of singular countable nouns, but we can use the with any noun and when it is clear which one we mean.
Examples:
     A dog is an animal. (dog and animal are singular countable nouns.)
     The dog barking at John is my neighbour's dog. (It is clear which dog we mean.) 

A question tag is a short question added on to a statement.  When a tag is spoken, the voice can go down or up.  We often use a question tag at the end of a sentence when we ask for agreement. 

This, that, these, those are pointing words called demonstratives.  This and these refer to something close by or near the speaker.  That and those refer to something further away.  This and that are singular.  These and those are plural.

We can use many different verb forms in conditional sentences.  Conditions express different degrees of reality.  In open conditions, we use the present to refer to the future.  When we talk about something unreal, we often use the past.

We can use conditional sentences in a number of different ways, e.g. to advise, suggest, offer, request, criticize, warn or threaten.