Mastering English Grammar: Perfect Tenses, Gerunds, Infinitives, and Modals

Present Perfect Continuous

AFF (Affirmative): Subject + have/has been + V.-ing

NEG (Negative): Subject + have/has not + been + V.-ing

INT (Interrogative): Have/Has + Subject + been + V.-ing

Uses:

• Actions that started in the past and are still continuing.
• Actions that have finished recently.

Expressions: for a year, since 2002, how long...?, all night...

Past Perfect Continuous

AFF (Affirmative): Subject + had been + V.-ing

NEG (Negative): Subject + had not been + V.-ing

INT (Interrogative): Had + Subject + been + V.-ing

Uses:

• To talk about a prolonged action that occurred in the past before another brief action.

Expressions: for hours, since last year, all morning, when, until, before...

Gerunds

A verbal form ending in -ing that functions as a noun in the following cases:

• As a direct object (DO) of some verbs: continue, deny, detest, dislike, enjoy, finish, hate, like, love, miss, prefer, recommend, suggest, etc.
• After prepositions.
• After some verbal forms: be used to/get used to, can't help, can't stand, don't mind/wouldn't mind, feel like, it's no use, look forward to, spend (time), etc.
• As the subject of the sentence when talking about actions or facts in general.

Infinitives

A verbal form that goes after "to", used in the following cases:

• As a subject, talking about a specific fact.
• After verbs such as: agree, appear, choose, decide, hope, learn, plan, promise, refuse, seem, try, want, wish, expect, manage, etc.
• After some adjectives (busy, happy, ready, tired, willing, etc.) and adverbs (slowly, fast, low, etc.).

Modal Verbs

Can

(Only in present simple)

• Ability
• Making requests
• Giving and asking for permission
• Making suggestions
• Indicating possibility

Be able to

Same as can, but used with other verb tenses.

Can't

• Lack of ability
• Prohibition
• Expressing that something is impossible

Could

• Ability in the past
• More polite requests
• Less direct suggestions
• More remote possibilities

May/Might

• Possibility of something happening (might is more remote)
• May is used to give, ask for, or deny permission, or to make polite requests.

Should/Ought to

• Giving advice and making recommendations.
• Ought to is rarely used in negative and interrogative forms; should is more common.

Need to/Needn't

• Need to is used in affirmative sentences to express obligation and necessity, similar to have to.
• Needn't indicates absence of obligation and necessity, similar to don't have to.

Must/Have to

• Expressing obligation or necessity.
• Must is only used in the present tense, and have to is used in other tenses.
• Must indicates authority and is used to draw a logical conclusion about a present fact.

Mustn't

Indicates prohibition.

Don't have to

Expresses absence of obligation and necessity.

Would

• In interrogative form, it is used to ask someone to do something.
• With like, it is used to make offers or invitations.

Shall

• In interrogative form, it is used to offer to do something and to make a suggestion.

Modal Perfects

Must have + participle

Expresses a logical conclusion about a past fact.

May/Might have + participle

Makes a supposition about a past fact, expressing the possibility that something was true.

Could have + participle

Indicates that something could have been done in the past, but it was not done.

Couldn't have + participle

Expresses certainty that something could not have happened.

Would have + participle

Indicates that someone wanted to do something in the past, but could not due to external circumstances.

Should/Ought to have + participle

Complains about what happened, regretting that what was expected did not happen.

Shouldn't have + participle

Expresses a critical action about a past fact, indicating that it should not have happened.

Needn't have + participle

Indicates that there was no need to do what was done.