by itself

by itself — 片語

1. happening or operating without anyone having to control, start, or stop it direc

1.片語B1
釋義

自動地

無需人為操作即自行運作

happening or operating without anyone having to control, start, or stop it directly — used mainly for machines, devices, and systems that run on their own.

例句

The front door unlocks by itself when you walk up to it with the key fob.

前門在你拿著鑰匙感應器走近時會自動解鎖。

describes a machine function triggered by a condition

The sprinkler system turns on by itself when the soil moisture drops below a certain level.

當土壤濕度低於一定標準時，灑水系統會自行啟動。

同義詞
  • automatically

    the more common adverb for this idea; slightly broader in use

  • on its own

    informal equivalent, very common in everyday speech

反義詞

用法筆記

Subject is always a thing (machine, device, system), never a person. For people doing something without help, use 'by oneself' (e.g., 'He fixed it by himself').

常見錯誤

⚠️ 'The computer turned off by itself' vs. 'The computer turned off automatically / on its own' — All three are natural for self-operating machines, so no correction is needed. 'Automatically' is the most formal; 'on its own' is the most informal.

2. with nothing or no one else nearby; without help from anyone or anything else —

2.片語A2
釋義

獨自；單獨

附近沒有其他人或物

with nothing or no one else nearby; without help from anyone or anything else — used to describe something that is physically isolated or an action done without assistance.

例句

The old farmhouse stood by itself at the end of a long, dusty road.

那棟老舊的農舍獨自矗立在一條漫長而塵土飛揚的道路盡頭。

describes physical isolation of a building

The children finished their homework by themselves while their father cooked dinner.

孩子們在父親煮晚餐的時候自己完成了作業。

同義詞
  • alone

    more common for people; does not change form for subject

  • unaided

    formal; emphasises the lack of assistance

  • on its own

    informal and very common for both things and people

反義詞

用法筆記

For things: describes physical isolation ('a tree standing by itself'). For people and animals: inflects to match the subject — by myself, by yourself, by himself, by herself, by ourselves, by yourselves, by themselves. This is the sense that most commonly takes each reflexive form.

常見錯誤

❌She sat by itself in the corner.
✅She sat by herself in the corner.
💡'by itself' is for things; use the matching reflexive for people.
❌He carried the box by itself.
✅He carried the box by himself.
💡When the subject is a person, the pronoun must agree with the subject, not the object.