There are about a million ways to talk about going to the toilet in English. There a different verbs to mean going to the toilet, lots of different words for what comes out, and even a few different words for the room and the toilet itself.
When you begin potty training, or toilet training, your children there are a few different ways to talk about needing the loo/toilet.
So very young children might say; I need potty. I need toilet. I need wee-wee. Adults might ask; Do you need (the) potty? Do you need a wee-wee?
Older children who can make longer sentences might say: I need to go to the potty, or I need to go to the toilet.
Pee, wee, or wee-wee are used by children to mean the verb and the noun. You might also hear when speaking to children: spend a penny, or go number one, or tinkle.
Urine (an uncountable noun) and the verb to urinate are used by doctors or in more formal situations.
Adults might refer to: taking a piss, having a slash, taking a leak which are informal and considered crude.
These are more polite but informal ways to say you need the toilet: To powder your nose, to go to the little boys’ room/ little girls’ room, to excuse yourself, or just ‘to go’. In everyday language you can just say Excuse me. Or with family and friends, I’m going to the toilet, or I need the toilet.
In the UK, potty means just the small pot that children learn to pee in. Toilet is used for the thing that you pee into, and the room itself too.
Where is the toilet? is fine to ask in British English in a restaurant, cafe or pub.