Strictly it is about grammar and usage. The rule of grammar is that a sentence must make complete sense. However, usage involves, implied statements, idiomatic expressions, and context.
Grammar then is like the skeleton and usage is like the flesh.
'It's a cravat, child, and a beautiful one, as you say. It's a present from the White King and Queen. There now!'
'Is it really?' said Alice, quite pleased to find that she had chosen a good subject after all.
'They gave it me,' Humpty Dumpty continued thoughtfully as he crossed one knee over the other and clasped his hands round it, 'they gave it me — for an un-birthday present.'
'I beg your pardon?' Alice said with a puzzled air.
'I'm not offended,' said Humpty Dumpty.
'I mean, what is an un-birthday present?'
'A present given when it isn't your birthday, of course.'
Alice considered a little. 'I like birthday presents best,' she said at last.
'You don't know what you're talking about!' cried Humpty Dumpty. 'How many days are there in a year?'
'Three hundred and sixty-five,' said Alice.
'And how many birthdays have you?'
'And if you take one from three hundred and sixty-five what remains?'
'Three hundred and sixty-four, of course.'
Humpty Dumpty looked doubtful. 'I'd rather see that done on paper,' he said.
Alice couldn't help smiling as she took out her memorandum book, and worked the sum for him:
Humpty Dumpty took the book and looked at it carefully. 'That seems to be done right —' he began.
'You're holding it upside down!' Alice interrupted.
'To be sure I was!' Humpty Dumpty said gaily as she turned it round for him. 'I thought it looked a little queer. As I was saying, that seems to be done right — though I haven't time to look it over thoroughly just now — and that shows that there are three hundred and sixty-four days when you might get un-birthday presents —'
'Certainly,' said Alice.
'And only one for birthday presents, you know. There's glory for you!'
'I don't know what you mean by "glory",' Alice said.
Humpty Dumpty smiled contemptuously. 'Of course you don't — till I tell you. I meant "there's a nice knock-down argument for you!"'
'But "glory" doesn't mean "a nice knock-down argument",' Alice objected.
'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.'
'The question is,' said Alice, 'whether you can make words mean so many different things.'
'The question is,' said Humpty Dumpty, 'which is to be master — that's all.'
(Alice Through the Looking Glass by Lewis Carroll)
Unfortunately that is not quite right, and the word you choose means what the reader thinks it means. This is because the meaning of a word is defined by its context. That is the whole point, there is an agreement as to what a word means, as say given in the dictionary, but the writer has to put the word in the correct context to convey with greater precision what he wants to say.