You aren’t half lucky to have Tim Bowen giving you tips on word grammar …
Half is one of the most multi-functional words in English, being used as a pre-determiner, a pronoun, an adjective, an adverb, a countable noun and a numeral. Within these categories it has some interesting uses. It can be used to mean ‘partly’, as in ‘Perhaps he half realized there was nothing more he could do’ or ‘The rocks were half under the water’. It can also be used with both adjectives and nouns for emphasis, as in ‘Your mother has been going half crazy worrying about you’ or ‘I seem to spend half my life cleaning up after those kids’.
In British English, the response Not half! is used both for emphasis with adjectives, as in ‘We weren’t half lucky to win that match’ or ‘I wasn’t half tired after work today’, and to emphasize that you really like something, as in ‘Do you like Italian food?’ ‘Yeah, not half!’.
If you go halves with someone, you split the cost of it, as in ‘If we’re going halves, we can afford a really nice bottle of wine’.
The term half the battle is used to refer to the most important part of what you have to do in order to achieve something, as in ‘Winning people’s trust is half the battle’.
Your other half is used to refer to your husband, wife or romantic partner, as in ‘I’d like to come tonight but I’ll have to ask my other half first’.
Used with adjectives that describe negative characteristics, the expression by half is used to show that you do not approve of someone because their behaviour annoys you, as in ‘He’s too eager by half. He needs to calm down a bit’.
A half-wit is an impolite term for someone who is stupid, and if an idea is half baked then it is not really thought through properly, as in, ’That half baked idea of hers is never going to work.’
Half time is the mid point in a game of football when both sides stop for a short break. Similarly, half way is the middle point between two places, for example, ’They stopped at the village because it was half way to the sea.’