According to the definition of the noun 'sex' in dictionaries, it means 'the PHYSICAL ACTIVITY that two people do together in order to produce babies or for pleasure.' If so, why isn't it countable?
'I had sex with her last night.' but not 'I had A sex / TWO sexes her last night.'
How do you count the activity? You go like 'I had sex with her twice.'?
I think that in general, a countable noun has a beginning and an end, viewed as a whole entity, while an uncoutable noun is undifferentiated and lacking in defined limits. Could the activity of sex continue no end? It must have a beginning and an end. The human can't do it forever even if he was cut out for it. Just saying the word is in itself an uncountable noun is a circular logic.
You could have A shag with her if you ask her out tomorrow.
why is 'shag' countable, while 'sex' is not? Both seem to refer to the same activity.
- Let's go for a drive.
- I take a shower every day.
- I had a walk in the morning.
- I'm going for a stroll.
All the nouns refer to activities, and are used with the indefinite article.
I really want to know what you have in mind about the interesting noun 'sex' and the reason why it isn't countable.