A meander around prefixes and suffixes, adjectives and adverbs:
One of the ways English works is to add bits on the front or back of a 'stem' or a 'root'. (a 'suffix' fixes things on the end, a 'prefix' fixes things on the front.)
'happy', 'unhappy', 'happiness', 'happily', 'unhappily'
'content', 'discontent', 'contented', 'discontent', 'discontentedly', 'contentedly'
'free', 'unfree', 'freedom', 'freely'
'fiend', 'fiendish', 'fiendishly', 'fiendishness'
'excel', 'excellent', 'excellence', 'excellently'
'satisfy', 'satisfaction', 'satisfactory', 'unsatisfactory,' 'dissatisfied', 'satisfied', 'satisfactorily', 'satisfying', 'satisfyingly'
You can also make up your own - comedians do it - and sometimes these become new usages. I don't think the word 'sweary' existed 20 years ago, but comedians started talking about 'sweary man' and the like and I often hear it. The suffix 'ish' can be added fairly easily too.
I'm not going to talk here about the 'rules' involved. I think the whole process is much too creative to label it like that. Perhaps there are several Ph.D's lying about which show how 'rule-governed' it all is. Perhaps so.
The reason why I'm bringing it up now is because we have coming over the horizon towards us, a consideration of 'adjectives' and 'adverbs'. The point about many suffixes is that we use them (or invent uses of them) so that we can 'describe' or 'modify' or 'add colour' to nouns and verbs. When we're doing it to nouns, 'the red balloon', we call them 'adjectives', when we do it to verbs 'I really like red balloons', we call them 'adverbs'.
1. Of course, there are some words which don't have suffixes that we can use for these purposes too: we usually use 'red' as an adjective, we usually use 'then' as an adverb.
2. Mysteriously and confusingly, the word 'adverb' is also used when adjectives are themselves modified eg with the word 'very' as in 'a very silly thing to say'. And, even more mysteriously and confusingly, when, it's said, a whole phrase, clause or sentence is modified:
'Happily for the team, Jim was fit.' (phrase)
'When, happily, the team was fully fit, they started winning a few games.' (clause)
'Eventually, the team was fit, and they started winning.' (sentence)
3. Whole phrases and clauses can behave 'adjectivally' and 'adverbially'. Teachers, this is the stuff that you're supposed to teach in order to improve writing. (You'll detect my scepticism in the way I put that.) The idea is that you should be encouraging the children to make their sentences more 'complex' or just plain longer, by not only adding adjectives and adverbs but also by adding in adjectival and adverbial phrases and clauses.
So, let's look at a sentence getting longer and longer - just for fun.
'The man was eating an apple.'
'The tall man was eating a blue apple.' (two adjectives added to the two nouns)
'The tall man was hurriedly eating a blue apple.' (adverb modifying 'was eating')
''Surprisingly, the tall man was hurriedly eating a blue apple.' (adverb modifying the whole sentence)
'When I walked in, surprisingly the tall man was hurriedly eating a blue apple.' (an adverbial clause added 'when I walked in')
'When I walked in, surprisingly the tall man who I saw in the lift, was hurriedly eating a blue apple.' (an adjectival clause added: 'who I saw in the lift')
'When I walked in for the second time, surprisingly the tall man who I saw in the lift, was hurriedly eating a blue apple' (adverbial phrase added: 'for the second time')
'When I walked in for the second time in a week surprisingly the tall man who I saw in the lift was hurriedly eating a blue apple.' (adjectival phrase added: 'in a week')
That's the grammar. As you can see, good writing doesn't happen simply by adding this sort of thing.