1
a tortoise
不定冠词 a 用于单数可数名词，这里 a tortoise 泛指陆龟这一类动物。
A tortoise can retract its head into its shell.
陆龟可以把头缩进壳里。
陆龟
先理解核心含义，再看它在真实句子里的用法。
陆龟
a slow-moving land turtle with a hard shell
A tortoise can retract its head into its shell.
陆龟可以把头缩进壳里。
陆龟(陆栖龟类,体被甲壳,头与四肢可缩入壳内)
Any of various land-dwelling reptiles, of the family Testudinidae (chiefly Canada, US) or the order Testudines (chiefly UK, Australia, New Zealand, Ireland, South Africa, India), whose body is enclosed in a shell (carapace plus plastron). The animal can withdraw its head and four legs partially into the shell, providing some protection from predators.
通常为草食性的陆龟,具有象脚般的爪子,分布于除澳大利亚和南极洲外的干旱地区
usually herbivorous land turtles having clawed elephant-like limbs; worldwide in arid area except Australia and Antarctica
同“cat”(带轮子的掩体)
Synonym of cat (sense 11, a wheeled shelter)
The tortoise slowly crossed the enclosure to reach the lettuce.
那只陆龟慢慢地穿过围场去够生菜。
My neighbor keeps a tortoise in her backyard and feeds it fresh vegetables every day.
我的邻居在后院养了一只陆龟，每天喂它新鲜蔬菜。
Unlike sea turtles, tortoises live entirely on land and dig burrows to stay cool.
与海龟不同，陆龟完全生活在陆地上，还会挖洞保持凉爽。
不定冠词 a 用于单数可数名词，这里 a tortoise 泛指陆龟这一类动物。
A tortoise can retract its head into its shell.
陆龟可以把头缩进壳里。
复数形式 tortoises 表示整个类别，作主语时谓语用复数。
Tortoises are generally herbivorous and live on land.
陆龟通常草食，生活在陆地上。
as slow as a tortoise 是习语，形容极慢，呼应 tortoise 的引申义“行动迟缓的人”。
He is as slow as a tortoise when doing his homework.
他做作业时慢得像只乌龟。
Not this
I have two tortoise in my garden.
Use this
I have two tortoises in my garden.
tortoise 是可数名词，两只以上要用复数 tortoises。这个错误来自汉语名词没有复数变化，直接说 two tortoise。
Not this
I saw a tortoise in the ocean.
Use this
I saw a sea turtle in the ocean.
tortoise 指陆龟，生活在内陆；海里的是海龟，要用 sea turtle。学习者常把中文“乌龟”一律译成 tortoise，但海龟并不是 tortoise。
Not this
Tortoise is a popular pet.
Use this
Tortoises are popular pets.
tortoise 是可数名词，表达“这一类动物”的泛指时要用复数或 a tortoise，不能用零冠词单数。汉语“乌龟很受欢迎”没有复数，所以容易漏掉复数。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
巨龟
The giant tortoise can live for over a hundred years.
巨龟可以活一百多年。
龟甲
The tortoise shell protects it from predators.
龟甲保护它免受捕食者伤害。
龟兔赛跑
The tortoise and the hare teaches us that perseverance pays off.
《龟兔赛跑》告诉我们坚持不懈会有回报。
陆龟
A land tortoise needs a dry, warm environment.
陆龟需要干燥温暖的环境。
像乌龟一样慢
He walked as slow as a tortoise.
他走路像乌龟一样慢。
宠物龟
A pet tortoise can be a long-term companion.
宠物龟可以成为长期的伙伴。
龟兔赛跑
Our team isn't the fastest, but this is the tortoise and the hare—we'll win by steady progress.
我们团队不是最快的，但这就是龟兔赛跑——我们会靠稳步前进取胜。
慢得像乌龟一样
After the update, my phone is as slow as a tortoise.
更新之后，我的手机慢得像乌龟一样。
《龟兔赛跑》——伊索寓言，比喻稳扎稳打者胜于急于求成者。
In the fable, the tortoise wins the race by keeping a steady pace.
在这个寓言中，乌龟靠保持稳定的步伐赢得了比赛。
Use tortoise naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
把 tortoise 记成‘托特斯’：想象陆龟托着沉重圆壳，一步一步慢吞吞地走。
语域：neutral 常见场景：动物科普、自然观察、日常聊天 tortoise 表示陆龟，是比较常见的中性词，日常交流、科普文章和学校教育中都能用；形容人行动迟缓是比喻用法，多用于口语。
与 tortoise /ˈtɔrtəs/ 真正押韵的是 mortise /ˈmɔrtəs/。porpoise /ˈpɔrpəs/ 的 -poise 与 tortoise 的 -toise 一样弱读为 /əs/，但不是全词押韵。拼写相近的 noise /nɔɪz/、poise /pɔɪz/ 和 turquoise /ˈtɜrkwɔɪz/ 中的 -oise/-quoise 读 /ɔɪz/，和 tortoise 不同；fortress /ˈfɔrtrəs/ 形近，但中间是 /tr/，也不押韵。
Dictionary facts from ECDICT, WIKTIONARY.