tortoise指的是在陸地上生活的龜。如果你放一缸水，把龜丟進(jìn)去會淹死的話，那它就是陸龜。
turtle指的是在水里生活的龜，或者至少是半水生。
由于生活環(huán)境不同，所以它們的四肢也有區(qū)別：
- tortoise一般具有短小強健的腿（short and sturdy feet with bent legs）
- turtle需要游泳所以一般都有腳蹼（webbed feet）,為了能勾住河堤上岸一般還有長爪（long claws），海龜?shù)脑挻蟛糠侄甲兂肾挔钪╢lipper）
另外還有個比較少用的詞叫terrapin，實際上是turtle的一種，本來只是指北美地區(qū)一種比較小的淡水龜，后來又在英國流行起來，把所有的淡水（fresh water）或者苦咸水（brackish water）里生活的龜叫做terrapin，管海龜叫turtle。所以，我的建議是能不用就別用這個詞兒了~
說了這么多，那我們經(jīng)常見到的巴西龜跟草龜應(yīng)該叫tortoise還是turtle呢？顯然應(yīng)該是turtle。
- 草龜（中國池塘龜）：Chinese pond turtle
- 巴西龜（紅耳龜）：red-eared slider turtle/terrapin，也可以簡稱red-eared slider
巴西龜名字里的這個slider比較有意思，參見維基百科里的解釋：
The "slider" in their name comes from their ability to slide off rocks and logs and into the water quickly.
參考：
http://www.diffen.com/difference/Tortoise_vs_Turtle
http://www.totallytortoise.com/tortoise-turtle-terrapin.html
https://en.wikipedia.org/wiki/Red-eared_slider
https://en.wikipedia.org/wiki/Chinese_pond_turtle
參考：https://en.wikipedia.org/wiki/Terrapin
A terrapin is one of several small species of turtle living in fresh or brackish water.
It appears that it became part of common usage during the colonial era of North America and was carried back to Great Britain. Since then, it has been used in common names for turtles in the English language.
