儿童篇
Do you need to go potty? 你要去大/小便吗？
I have to pee-pee. 我要小便了。
May I go poop-poop? 我能去大便吗？
Take off your pants. 把你的裤子脱下来。
Remember to lift up the toilet seat. 记得把马桶座圈掀起来。
I need to go to the bath room. 我要去一下洗手间。
Don’t unroll the toilet paper. 不要把抽开那个卷纸。
Wipe your bottom. 给你擦屁屁。
Poop is stinky, so we need to flush the toilet. 便便很臭，所以我们要冲一下马桶。
You have to wash your hands with soap/liquid soap. 你要用肥皂/洗手液洗手。
I'll air out the room. 我会通风的。
to make a BM.The boy had a stinky BM.（大便奇臭。）
成人篇
几种想去卫生间的表达
I need to go to somewhere.
I want to wash my hands./ I need to powder my nose(搽点粉)./I need to fix my face.（女生多用）
I want to/need to go to/use the bathroom.
I need to answer the call of nature.(更为文雅)
I need to make a pit stop(赛车中紧急维修点).（年长女士）
I need to go pee. / I need to take a leak./ I need to take a dump.(粗鲁讲法，教育程度不高)
I want to get/have some fresh air.
卫生间、大解、小解等的不同的表达
之一：厕所
美国
restroom
bathroom
washroom
men's room=gent's room
ladies' room=powder room
lavatory(飞机上)
latrine(军中)
英国
toilet
loo(May I use your loo?)
偶尔W.C.(water closet)
几乎不用bathroom，因为英国传统居民住房是最普遍的semi-detached house（两家挨在一起的房子），分上下两层，上层主人使用，洗手间内有卫浴设施；下层洗手间给客人使用，一般只有马桶和洗手池。
其他
(portable) john 指户外的流动型厕所
之二：小解
to urinate = to piss = to take a piss = to take a leak = to void = to empty
相关例句
护士：Could you urinate in this cup？
医生：Do you have trouble urinating?=Do you have difficulty voiding?(小解有困难吗？)
The manual labours have to use (portable) johns during their working hours.（劳动者在工作时间内需要使用流动性厕所。）
如果「小便」有毛病，也可以告诉医生说：
My urine is cloudy and it smells strong.（有浊尿，味道很重）
I have pus （或air）in urine.（尿有泡沫） （pus = cloudy; air = bubble）
I dribble a little urine after I have finished urinating.（小便后还会滴滴答答。）（即失禁毛病）
I am passing less urine than usual.（小便的量比平时少）
相关词组
urine test 小便检查
to piss off 是指对人生气或对事物的不满。不礼貌的片语，少用为妙。
如： He pissed me off. = He made me angry.
He always pisses off （at） the society.（对社会不满）
之三：大解
to make/have a bowel movement = to take a shit=to defecate =to discharge excrement['ekskrɪm(ə)nt]
（或 feces['fiːsiːz]）=to take feces （或 faeces）
相关例句和词组
医生：Do you have regular bowel movement？（大便正常吗？）
stool exam 大便检查
俚语
go to a bank
go see a dog
feed a dog
shoot the dog
go to feed the goldfish
之四：放P
to expel gas = to fart = to make / pass gas
相关例句
医生有时问：How often do you expel/make/pass gas？（你放P的次数很多吗？）
Is the gas expelled by belching？（是否打嗝后就会放P呢？）
He said the more he ate, the more he farted.（吃的愈多，放P也愈多。）
Be careful not to fart in the public.（注意在公共场所不可放*。）
之五：消化不良等的说法
I have an upset stomach.（消化不良）= I have heartburn. = I have indigestion. 注意：Heartburn是指胃不舒服，不是「心痛」（heartache）。
Something has upset my stomach for two weeks.（胃不舒服有两星期了。）
He has（persistent）constipation.（或irregularity）（他经常便秘。)
He has been unusually constipated.（便秘很反常。）
He is having problem with irregularity.（或constipation)
He has no bowel movement for the past few days.
He has bouts of diarrhea[,daɪə'riə].=He is having trouble with diarrhea.（他拉了一阵肚子。）
He can see trace of blood and pus or mucus in his stool（或bowel movement）（大便时可看到血丝和粘膜。）
参考资料：李孔敬的日志、可可英语、百度。如有侵权，请立马联系作者告知，谢谢！
