necessary

necessary — adjective

1. Something that you must have, or that must happen, so that a particular result c

1.形容詞A2
釋義

Something that you must have, or that must happen, so that a particular result can be achieved or a situation can exist.

例句

A valid passport is necessary if you plan to travel to most foreign countries.

n + be + necessary + if-clause

The hospital must buy the necessary equipment before the new wing opens.

the necessary + noun (equipment)

同義詞
  • essential

    stronger than 'necessary'; suggests something is at the very core of the activity

  • required

    more concrete and rule-based; often used for official needs

  • obligatory

    formal; refers to something demanded by a law or rule

反義詞
  • unnecessary

    not needed; the most direct opposite

  • optional

    available to choose or not; not at all required

文法句型

it is necessary to + infinitive

necessary for + noun/gerund

necessary + noun

用法筆記

Often used in the pattern 'it is necessary to + verb' or 'it is necessary that + clause'. The opposite is 'unnecessary'.

常見錯誤

❌It is necessary for me to going now.
✅It is necessary for me to go now.
💡after 'to', use the base form of the verb, not the -ing form.
❌It is necessary that he comes tomorrow.' (informal)
✅It is necessary that he come tomorrow.
💡in formal English, the subjunctive (no -s) is used after 'that'.

2. Used in negative statements and questions when you think something is wrong, exc

2.形容詞B1
釋義

Used in negative statements and questions when you think something is wrong, excessive, or not worth doing.

例句

Was it really necessary to spend so much money on a hotel room?

question: Was it really necessary to...?

All this extra packaging is not necessary — the product would be fine without it.

not necessary for criticizing something

同義詞
  • pointless

    stronger criticism; suggests the action has no purpose at all

  • unjustified

    formal; suggests the action has no reasonable basis

文法句型

not necessary

Is/Was it really necessary to...?

用法筆記

The disapproval is carried by context and tone, not by the word 'necessary' alone. 'Not necessary' can simply mean 'not required' in a neutral sense — the critical reading comes from the situation described.

常見錯誤

❌It wasn't necessary to lock the door because there was nothing valuable inside.' (used neutrally, but may sound critical)
✅There was no need to lock the door.
💡for a neutral statement about lack of need, 'no need' avoids the possible critical tone.

3. Certain to happen because of the way a situation has developed; impossible to pr

3.形容詞B2
釋義

Certain to happen because of the way a situation has developed; impossible to prevent or avoid.

例句

Higher prices are the necessary result when the cost of materials goes up.

the necessary result

The scientist accepted the failed experiment as a necessary step on the path to discovery.

同義詞
  • inevitable

    more common in everyday language; means the same thing

  • unavoidable

    emphasises that no action could have prevented it

  • inescapable

    stronger and more dramatic; suggests something cannot be evaded

反義詞

文法句型

necessary + noun (result/consequence/outcome)

用法筆記

This sense is most common with nouns like 'result', 'consequence', 'outcome', and 'part'. It is rarely used in everyday speech — 'inevitable' sounds more natural in casual contexts.

necessary — noun