厕所
在美国一般都叫rest room或bath room(男女厕均可)或分别叫做 men‘s room 或 ladies‘ room(=powder room)，不过在飞机上，则叫 lavatory，在军中又叫 latrine。至于 W.C.(water closet)仍是过去英国人用的，在美国，几乎没有人使用。
解小便
最普通的说法是 to urinate(名词是 urination)，如果去看病，护士为了化验小便，就会给你一个杯子说：「Will (could) you urinate in this cup?」医生或许也会问：「Do you have trouble urinating?」=Do you have difficulty voiding?(小便有困难吗?)
此外，还有其他的说法：to piss = to take a piss = to take a leak = to void = to empty。 例如：
I need to piss = I have to take a leak.
How often do you get up at night to void?(晚上起床小便几次?)
此外，john(j 小写时，不是男人名字)是 bath room 或 toilet 的意思(也叫 outhouse)，这通常是指在户外工作场地所使用的临时或流动性厕所(有时前面也加 portable 一字)。不过也有老外把家里的厕所叫做 john。 例如：
There are several (portable) johns in the construction site.(在建筑场地有几个临时厕所。)
He went to the john a few minutes ago.(他在几分钟前上了厕所。)
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。)
不过，小孩多半用 to pee 。例如：The boy needs to pee.
然而，「小便检查」又叫做 urine test，因为这里的 urine 是化验的样品(specimen)。 例如：Do I need a urine test?
注意：to piss off 是片语，又是指对人生气或对事物的不满。不过这是不礼貌的片语，少用为妙。 例如：
He pissed me off. = He made me angry.
He always pisses off (at) the society.(对社会不满)
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)
解大便
一般是用 to make(或 have)a bowel movement 或 to take a shit。如果看病，医生常问：「Do you have regular bowel movement?」(大便正常吗?)(说得斯文些，就是「大肠在转动」)
此外，还有其他的说法： to defecate =to discharge excrement(或 feces)=to take feces (或 faeces)。 例如：
The patient needs to take a shit. (=to make a bowel movement)
不过，小孩多半是用 to make a poo poo 或 to make a BM. 。 例如：
The boy had a stinky BM.(大便奇臭。)
但是「大便检查」倒叫做 stool exam，因为 stool 也是一种化验的样品。 例如：
The doctor has to exam his stool.(医生要检查他的大便。)
放屁
在美语里最常用的是 to expel gas 或 to fart 或 to make (或 pass)gas。 例如：
医生有时问：「How often do you expel(或 make 或 pass)gas?」(你放屁的次数很多吗?)
Is the gas expelled by belching?(是否打嗝后就会放屁呢?)(动词是 belch)
He said the more he ate, the more he farted.(吃的愈多，放屁也愈多。)
He has passed more gas than usual within the last two days.(过去两天中，他放屁比平常多。)
Be careful not to fart in the public.(注意在公共场所不可放屁。)
至于消化不良，大便不通或拉肚子，也有不同的说法。 例如：
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。) 或
He has been unusually constipated.(便秘很反常。)或
He is having problem with irregularity.(或 constipation); 或 He has no bowel movement for the past few days.
He has bouts of diarrhea.=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。)
