before

• 副词，表示“在更早的时间”或“在过去”。用于指某一特定时刻之前的时间，常不指明具体时间。

An adverb meaning 'at an earlier time' or 'in the past.' It is used to refer to a time preceding a specific point in time, often without specifying exactly when.

1. Earlier in timeA1formal

   At a previous time; previously.

   以前

   • I have seen this movie before.
   • She had visited Paris before.
   • He arrived before the meeting started.

   同义词aheadbeforehandformerlypreviously

   反义词after

2. In front or aheadA2formal

   At or in the front; in a forward position.

   在前面

   • The guide walked before, leading the group.
   • The car before suddenly stopped.
   • He stood before the crowd to speak.

   同义词aheadforwardin frontin the lead

   反义词afterbehind

• 引导时间状语从句的连词，表示主句动作发生在从句动作之前，也可表示防止或优先。

A subordinating conjunction primarily used to introduce a dependent clause indicating that the action or state expressed in the main clause occurs earlier in time than the event described in the subordinate clause. 'Before' establishes a clear chronological precedence and is one of the most fundamental temporal markers in English syntax. Beyond strict chronology, it frequently conveys pragmatic meanings such as prevention, preparation, or proactive avoidance, where the main clause action is taken specifically to mitigate or forestall the subsequent event. In formal, literary, or rhetorical contexts, 'before' can also express strong preference, moral priority, or emphatic concession, often appearing in comparative structures. It follows standard adverbial clause punctuation rules: a comma is typically required when the 'before'-clause precedes the main clause, but omitted when it follows. The conjunction is universally recognized across all dialects and registers, and is acquired at the earliest stages of language acquisition.

1. Introducing temporal precedence: event A occurs prior to event BA1informal

   Used to introduce a subordinate clause that specifies a point in time following which the action of the main clause occurs. The conjunction 'before' establishes a clear chronological order: the event in the main clause happens first, and the event in the 'before'-clause happens subsequently. This is the primary and most frequent function of 'before' as a conjunction. Tense relationships typically follow standard sequence-of-tenses conventions: past simple or past perfect in the main clause paired with past simple in the 'before'-clause for completed sequences, or present/future reference in the main clause with present simple in the 'before'-clause for future temporal sequences. Punctuation requires a comma when the 'before'-clause precedes the main clause, but no comma is needed when the main clause comes first.

   表示时间上的先后：事件A发生在事件B之前

   • Please close the door before you leave the room.
   • She finished her advanced degree before moving to London for work.
   • Check your laboratory equipment carefully before starting the experiment.
   • The sun had already set before they finally reached the remote campsite.
   • We need to submit the grant proposal before the official deadline passes.

2. Expressing prevention, preparation, or proactive avoidanceB1informal

   Used to indicate that the action in the main clause is undertaken specifically to prevent, prepare for, or mitigate the event described in the subordinate clause. In this functional extension, 'before' carries a pragmatic implication of caution, risk management, or anticipatory action rather than mere chronological sequencing. The temporal relationship remains structurally intact, but the semantic focus shifts toward purpose, safeguarding, or error prevention. This usage is highly prevalent in instructional, technical, advisory, and narrative contexts where foresight is emphasized.

   表示预防、准备或提前规避

   • Always secure your backups before installing the new software update.
   • He issued a formal apology before she could publicly voice her frustration.
   • The engineering team reinforced the structural supports before the storm made landfall.
   • Review the legal contract thoroughly before signing any binding documents.
   • She packed a waterproof jacket before stepping outside, anticipating sudden rainfall.

3. Marking rhetorical preference, moral priority, or emphatic concessionC1formal

   Employed in formal, literary, or rhetorical discourse to express a strong preference for one course of action over another, or to emphasize that one state or event must take absolute precedence over another. Often appears in constructions such as 'I would... before I...' or 'He would rather X before Y'. In this usage, 'before' functions less as a strict temporal marker and more as a preferential or concessive subordinator, highlighting moral, emotional, or logical priority. It creates rhetorical tension by framing the subordinate clause as an unacceptable or undesirable alternative that the speaker actively resists. This construction is characteristic of elevated prose, persuasive writing, and dramatic or diplomatic speech.

   表示修辞上的偏好、道德优先或强调性让步

   • I would resign immediately before compromising my core ethical principles.
   • She would trek across frozen terrain for days before admitting she needed assistance.
   • The organization would restructure its entire hierarchy before accepting external interference.
   • He would rather face a formal tribunal before offering a public apology to his rivals.
   • The community would rebuild its infrastructure from scratch before surrendering to administrative control.

• 介词 'before' 表示时间、顺序或位置上的先于；指在某个事件、时间或人之前，或在空间或地位上位于某人/某物前面。

The preposition 'before' indicates precedence in time, order, or position; it refers to a point earlier than a specific event, time, or person, or being in front of someone/something in space or rank.

1. Time: Earlier thanA1formal

   Indicates a point in time that is earlier than a specific event, date, or moment

   在……之前

   • Please arrive before 9 AM
   • She left before the end of the movie
   • Wash your hands before eating

2. Order: Preceding in sequenceA2formal

   Indicates a position in a sequence, list, or queue that comes prior to another

   在……之前

   • B comes before C in the alphabet
   • Your name is before mine on the list
   • Dinner before dessert, please

3. Position: In front ofA2formal

   Indicates spatial position where someone or something is located in front of another person or object

   在……前面

   • He stood before the judge
   • The car stopped before the crosswalk
   • She knelt before the statue

4. Preference: Rather thanB1formal

   Used to express a preference for one option over another

   宁愿，而不是

   • I would choose death before dishonor
   • She prefers tea before coffee
   • He put work before family

5. Priority: More important thanB2formalbusiness

   Indicates that one thing is considered more important or has higher priority than another

   优先于，重于

   • Safety comes before speed
   • He puts his children before himself
   • Business before pleasure

6. Presence: In the presence ofB2formallegal

   Indicates being in the presence or view of someone, often implying formality or authority

   在……面前

   • The vow was made before witnesses
   • He appeared before the committee
   • Do not speak before the king