One / ones is used to avoid repeating a countable noun, but there are some times when you should not use it, especially in formal speech or writing. * one/ones 用以避免重复可数名词；但有时候，尤其在正式谈话或书面语中，不应使用：

• After a possessive (my, your, Mary's, etc.), some, any, both or a number, unless it is used with an adjective. 在所有格（如 my、your、Mary's 等）、some、any、both 或数字之后不用 one/ones，除非与形容词连用：◆'Did you get any postcards?' 'Yes, I bought four nice ones.' “你买明信片了吗？” “买了，我买了四张很漂亮的。”◆I bought four ones.
• It can be left out after superlatives, this, that, these, those, either, neither, another, which, etc. 在形容词最高级、this、that、these、those、either、neither、another、which 等词后可省略 one/ones：◆'Here are the designs. Which (one) do you prefer?' 'I think that (one) looks the most original.' “图样在这里。你喜欢哪（一）张？” “我认为那张看上去最有创意。”
• These ones and those ones are not used in NAmE, and are unusual in BrE. 美式英语中不用 these ones 和 those ones，英式英语也很少用：◆Do you prefer these designs or those? 你喜欢这些图样还是那些？
• It is never used to replace uncountable nouns and is unusual with abstract countable nouns: ◆The Scottish legal system is not the same as the English system is better than ◆…as the English one. * one/ones 不用以替代不可数名词，与抽象可数名词连用也很少见：用 The Scottish legal system is not the same as the English system（苏格兰法制与英格兰法制不同）胜于用 ... as the English one。