The four conditional patterns

The if-clause states the condition, usually in a present or past form; will and would normally belong to the main clause.

• Zero conditional (general truth): if + present simple, present simple. If water is heated to 100 degrees Celsius at sea level, it boils.
• First conditional (real future): if + present simple, will + base verb. If the list is released on Monday, we will begin verification.
• Second conditional (unreal present or future): if + past simple, would + base verb. If I were the controlling officer, I would sanction it. Were is the standard formal form for every person; if I was is informal.
• Third conditional (unreal past): if + had + past participle, would have + past participle. If he had read the circular, he would have applied in time.

If it will rain and if he would have known are wrong in standard written English. The narrow exceptions are will or would meaning willingness or polite request (if you will wait here, I will fetch the file; if you would sign here). They are rarely tested.

Mixed conditionals and inversion

A mixed conditional links a past condition to a present result: if she had cleared the interview, she would be serving in Hyderabad now. The reverse, a present condition with a past result, is also possible: if he were more careful, he would not have made that error.

Inversion: in formal English, if can be dropped and the auxiliary moved in front of the subject. Had he read the circular (third), were I in charge (second), should you need clarification (first, meaning “if you happen to need”). An inverted clause is already conditional, so adding if to it is an error (if had he read). Negatives are not contracted in inversion: had he not read, not hadn’t he read.

Unless, lest, no sooner, hardly

Unless means if not, so a further not is redundant: unless you apply, you will not be considered (not unless you do not apply).

Lest means “for fear that”, so it is already negative and never takes not. It is followed by should + base verb, or by the bare subjunctive: work carefully lest you should miss the deadline (also lest you miss). Exams prefer the should form; lest you will miss and lest you should not miss are errors.

No sooner pairs with than; hardly and scarcely pair with when (or before), never with than. When these adverbs open the sentence, the auxiliary comes before the subject, usually with the past perfect: no sooner had the meeting begun than the power failed; hardly had he left when the call came. Without inversion, the adverb follows the auxiliary: the meeting had no sooner begun than the power failed.

Wish, it is time, would rather

These structures use a past form to express an unreal or desired present. I wish I knew the answer (present regret); I wish I had known earlier (past regret). It is time, or it is high time, takes the past simple: it is high time the department cleared the backlog. Would rather with a different subject also takes the past: I would rather you submitted it today. With the same subject it takes the base verb: I would rather wait.

A or an: the sound rule

The choice depends on the first sound, not the first letter. An hour, an honest officer, an MBA, an FIR and an X-ray take an because each begins with a vowel sound (silent h; /em/, /ef/, /eks/). A university, a European delegation, a one-time settlement and a UPSC examination take a because each begins with a consonant sound (/j/ or /w/). Acronyms read as words follow their pronunciation: a NATO meeting.

Where the is required

The marks something specific or unique: the sun, the equator. It is used with rivers, seas, oceans, canals, mountain ranges, groups of islands and deserts (the Ganga, the Arabian Sea, the Suez Canal, the Himalayas, the Andaman Islands, the Thar); with superlatives and ordinals (the most experienced candidate, the first instalment); with country names that are plural or contain a common noun (the Netherlands, the Maldives, the United Kingdom, the USA); with musical instruments (she plays the sitar); with an adjective standing for a class (the poor, the unemployed); and with a singular noun representing a whole class (the tiger is a protected species). The secretary and treasurer refers to one person; the secretary and the treasurer refers to two, and the verb agrees accordingly.

Where no article is used

No article is used with single peaks and most lakes (Mount Everest, Dal Lake), with most country names, languages and games (India, Hindi, cricket), with meals in general (after lunch), and with institutions visited for their main purpose (go to school, go to bed, be in hospital). Plural lake groups take the (the Great Lakes). The article returns when the reference changes: the Hindi language; he went to the school to meet the principal; the lunch we had was excellent.

Few and little are negative in sense (hardly any), while a few and a little are positive (some). The few means “the small number that there are”: the few books he had were all borrowed.

Key points to remember

Frequently asked questions

What are the four types of conditional sentences?

Zero (if + present, present: general truths), first (if + present, will + base verb: real future), second (if + past, would + base verb: unreal present) and third (if + had + past participle, would have + past participle: unreal past). Mixed conditionals combine the second and third patterns.

How does inversion work in conditional sentences?

In formal English, drop if and put the auxiliary first: Had I known (= If I had known), Were I the Director (= If I were the Director), Should you need help (= If you need help). Do not keep if with an inverted clause.

Is “unless you do not” correct?

No. Unless already means if not, so adding not creates a double negative. Write “Unless you apply, you will not be considered.”

Which conjunction follows no sooner, hardly and scarcely?

No sooner is followed by than; hardly and scarcely by when. When they open the sentence, invert the auxiliary: No sooner had he arrived than it began to rain.

When do we use a or an?

By the first sound, not the letter: an hour, an honest man, an MBA, an FIR, but a university, a European, a one-way ticket, a UPSC exam.

Practice: 10 MCQs

Attempt all ten questions, then press Submit. The correct answer and a short explanation appear under every question, followed by your score analysis.

Verification notes

• Checked against Cambridge Dictionary’s English Grammar Today (conditionals; unless; lest; no sooner; hardly; inversion; articles; it’s time), British Council LearnEnglish grammar pages, and Swan, Practical English Usage (4th ed.).
• Each MCQ was tested for a single defensible answer under standard British/Indian written usage.