Understanding the correct usage of 
indefinite articles and abbreviations can be a challenge for both native and non-native English speakers. Should it be a MRI scan or an MRI scan; a UNESCO heritage site or an UNESCO heritage site? This post first describes the difference between acronyms and initialisms, before explaining the reason why we use an MRI scan, for example, despite the abbreviation beginning with a consonant.
When more than one adjective is used to 
modify a noun, or when nouns are used to modify another noun, the order of adjectives needs to follow a particular sequence. For example, we could say a delicious mature blue cheese but not a blue delicious mature cheese. This post defines the positions for different groups of adjectives with examples given.
This post explores the nature of homonyms as a word class. A definition and examples are given before moving on to consider polysemy, homographs and homophones, which are all part of the same word class family.