Active and Passive Voice

The active voice (where the verb's subject is understood to denote the doer, or agent), of the denoted action) is the unmarked voice in English.

To form the passive voice (where the subject denotes the undergoer, or patient), of the action), a periphrastic construction is used.

In the canonical form of the passive, a form of the auxiliary verb be (or sometimes get) is used, together with the past participle of the lexical verb. Passive voice can be expressed in combination together with tenses, aspects and moods, by means of appropriate marking of the auxiliary (which for this purpose is not a stative verb, i.e. it has progressive forms available).

For example:

• This room is tidied regularly. (simple present passive)
• It had already been accepted. (past perfect passive)
• Dinner is being cooked right now. (present progressive passive)

The passive forms of certain of the combinations involving the progressive aspect are quite rare; these include the present perfect progressive (it has been being written), past perfect progressive (it had been being written), future progressive (it will be being written), future perfect progressive (it will have been being written), conditional progressive (it would be being written) and conditional perfect progressive (it would have been being written). Because of the awkwardness of these constructions, they may be paraphrased, for example using the expression in the process of (it has been in the process of being written, it will be in the process of being written, and similar).

The uses of these various passive forms are analogous to those of the corresponding tense–aspect–mood combinations in the active voice.

Indirect Speech

Verbs often undergo tense changes in indirect speech. This commonly occurs in content clauses (typically that-clauses and indirect questions, when governed by a predicate of saying (thinking, knowing, etc.) which is in the past tense or conditional mood.

In this situation the following tense and aspect changes occur relative to the original words.

Changes to past:

• "I like apples." → He said that he liked apples.
• "We are riding." → They claimed that they were riding.
• "You have sinned." → I was told that I had sinned.

Changes to past perfect (and sometimes past progressive to past perfect progressive):

• "They finished all the wine earlier." → He thought they had finished all the wine earlier.

This change does not normally apply, however, when the past tense is used to denote an unreal rather than a past circumstance (e.g., expressions of wish, conditional sentences and dependent clauses):

• "I would do anything you asked." → He said he would do anything she asked.

Changes to conditional, also referred to as future-in-the-past (i.e. will/shall changes to would/should):

• "The match will end in a draw." → He predicted that the match would end in a draw.

The modals can and may change to their preterite forms could and might :

• "We may attend." → She told us that they might attend.

Verb forms not covered by any of the above rules (verbs already in the past perfect, or formed with would or other modals not having a preterite equivalent) do not change. Note that application of the above rules is not compulsory; sometimes the original verb tense is retained, particularly when the statement (with the original tense) remains equally valid at the moment of reporting:

• "The earth orbits the sun." → Copernicus stated that the earth orbits the sun.

Note also that the above tense changes do not apply when the verb of saying (etc.) is not past or conditional in form; in particular there are no such changes when that verb is in the present perfect: He has said that he likes apples.

Infinitive

Regarding English, the term infinitive is traditionally applied to the unmarked form of the verb when it forms a non-finite verb, whether or not introduced by the particle to.

Hence sit and to sit, as used in the following sentences, would each be considered an infinitive:

• I can sit here all day.
• I want to sit on the other chair.

The form without to is called the bare infinitive; the form introduced by to is called the full infinitive or to-infinitive.

The other non-finite verb forms in English are the gerund or present participle (the -ing form), and the past participle – these are not considered infinitives.

Moreover, the unmarked form of the verb is not considered an infinitive when it is forms a finite verb: like a present indicative ("I sit every day"), subjunctive ("I suggest that he sit"), or imperative ("Sit down!"). (For some irregular verbs the form of the infinitive coincides additionally with that of the past tense and/or past participle, like in the case of put.)

Certain auxiliary verbs are defective in that they do not have infinitives (or any other non-finite forms).

This applies to the modal verbs (can, must, etc.), as well as certain related auxiliaries like the had of had better and the used of used to. (Periphrases can be employed instead in some cases, like (to) be able to for can, and (to) have to for must.) It also applies to the auxiliary do, like used in questions, negatives and emphasis like described under do-support. Infinitives are negated by simply preceding them with not.

Of course the verb do when forming a main verb can appear in the infinitive. However, the auxiliary verbs have (used to form the perfect) and be (used to form the passive voice and continuous aspect) both commonly appear in the infinitive: "I should have finished by now"; "It's thought to have been a burial site"; "Let him be released"; "I hope to be working tomorrow."

Perfect Infinitive

There are nonfinite constructions that are marked for perfect, progressive or perfect progressive aspect, using the infinitives, participles or gerunds of the appropriate auxiliaries. The meanings are as would be expected for the respective aspects: perfect for prior occurrence, progressive for ongoing occurrence at a particular time. (Passive voice can also be marked in nonfinite constructions – with infinitives, gerunds and present participles – in the expected way: (to) be eaten, being eaten, having been eaten, etc.)

Examples of nonfinite constructions marked for the various aspects are given below.

Bare infinitive:

• You should have left earlier. (perfect infinitive; for similar constructions and their meanings see modal verbs)
• She might be revising. (progressive; refers to an ongoing action at this moment)
• He must have been working hard. (perfect progressive; i.e. I assume he has been working hard)

To-infinitive:

• He is said to have resigned. (perfect infinitive)
• I expect to be sitting here this time tomorrow. (progressive)
• He claims to have been working here for ten weeks. (perfect progressive)

Present participle:

• Having written the letter, she went to bed. (perfect)
• The man having left, we began to talk. (perfect, in a nominative absolute construction)
• Having been standing for several hours, they were beginning to feel tired. (perfect progressive)

Past participle:

• We have been waiting a long time. (progressive, used only as part of a perfect progressive construction)

Gerund:

• My having caught the spider impressed the others. (perfect)
• We are not proud of having been drinking all night. (perfect progressive)

Other aspectual, temporal and modal information can be marked on nonfinite verbs using periphrastic constructions. For example, a "future infinitive" can be constructed using forms such as (to) be going to eat or (to) be about to eat.

Clause

A clause is a grammatical unit built around a verb that typically contains a subject and a predicate. Understanding clauses is essential because they are the core building blocks of every sentence you read, write, or speak.

What makes a clause?

At minimum, a clause needs a verb (the predicate) and, in most cases, a subject — the person or thing the verb says something about. The predicate can also include objects, complements, and modifiers.

• She laughed. — subject (she) + verb (laughed)
• The manager approved the budget yesterday. — subject + verb + object + modifier

Sometimes the subject is left out. This happens regularly in imperative sentences and non-finite clauses:

• Sit down. — no visible subject, but "you" is understood
• Walking home, I noticed the shop was closed. — the -ing clause has no stated subject

Types of clauses

There are two main types:

• Independent clause (also called a main clause) — can stand on its own as a complete sentence. It contains a finite verb.

  • I missed the bus.

• Dependent clause (also called a subordinate clause) — cannot stand alone and needs an independent clause to make sense.

  • Because I overslept — incomplete on its own

Combine them and you get a complex sentence:

• I missed the bus because I overslept.

A simple sentence has one independent clause. More complex sentences combine independent and dependent clauses in various ways.

Quick check: If you can remove a group of words from a sentence and it still has a subject + finite verb and makes sense on its own, that group is likely an independent clause.

Why clauses matter

Recognizing clause boundaries helps you punctuate correctly, avoid run-on sentences, and build more varied, natural-sounding writing. Once you can spot where one clause ends and another begins, sentence structure becomes much easier to manage.

Ready to practice? Try Complex Sentence for the basics, then move on to Complex Sentence: Adverbials or Participle Clauses: Shortening Sentences with -ing and Having + Past Participle to deepen your skills.

Subject

The subject is the part of a sentence or clause that tells you who or what the sentence is about. It typically comes before the verb and controls the verb's form — meaning the verb must agree with the subject in number and person.

How to identify the subject

The subject is usually a noun, pronoun, or noun phrase that performs the action or is described by the predicate.

• She works at a hospital.
• The old bridge collapsed during the storm.
• Running every morning keeps me healthy.

The verb agrees with the subject: She works (singular) vs. They work (plural). This subject-verb agreement is one of the most reliable ways to find the subject.

Self-check trick: Ask "Who or what + verb?" to locate the subject. "Who works at a hospital?" → She. That's your subject.

Types of subjects

• Simple subject — the core noun or pronoun alone: Dogs bark.
• Complete subject — the simple subject plus all its modifiers: The two large dogs next door bark every night.
• Compound subject — two or more subjects joined by a conjunction: Coffee and tea are available.

Tricky cases

Sometimes the grammatical subject isn't the "doer." In passive sentences, the subject receives the action:

• ❌ Thinking the subject must be the doer: "The window" broke itself?
• ✅ The window was broken by a ball. (The window is the subject, but the ball did the breaking.)

English also uses dummy subjects — words like it or there that fill the subject position without carrying real meaning:

• It is difficult to learn French.
• There are three problems with this plan.

In the first example, the "real" subject (the thing that is difficult) is to learn French, but grammatically it holds the subject slot. These are sometimes called expletive subjects.

Why it matters

Getting the subject right is essential for subject-verb agreement, choosing correct pronoun forms (he vs. him), and building clear sentences. Misidentifying the subject is one of the most common sources of grammar errors, especially with longer or inverted sentences.

Practice identifying subjects and building correct sentences with challenges like Basics. Common Questions. and Basics. Pronouns and Possessives..

B2 | Upper Intermediate

B2, or Upper Intermediate, is the fourth level on the CEFR scale. It marks the point where you move from "getting by" to genuinely comfortable communication — handling complex topics, expressing nuanced opinions, and understanding most of what you read or hear in real-world contexts.

What a B2 user can do

At this level, you're expected to:

• Understand complex texts on both concrete and abstract topics, including technical discussions in your own field.
• Follow extended speech and lectures, even when the structure isn't entirely clear, as long as the topic is reasonably familiar.
• Interact fluently and spontaneously enough that conversations with native speakers flow naturally — without strain on either side.
• Produce clear, detailed text on a wide range of subjects, using connectors and cohesive devices to build well-structured arguments.
• Explain and defend a viewpoint on a topical issue, weighing the advantages and disadvantages of different options.
• Recognize implicit meaning — reading between the lines in demanding, longer texts.

What B2 grammar looks like in practice

B2 is where grammar stops being about isolated rules and starts being about flexibility and precision. You're expected to control structures like:

• Advanced conditionals and mixed conditionals — moving beyond simple if-clauses to express hypothetical and counterfactual meaning.
• Passive voice in varied tenses and contexts, not just present and past simple.
• Reported speech with correct sequence of tenses, including backshifting and reporting verbs.
• Participle clauses and the distinction between participles and gerunds.
• Comparative and superlative structures beyond basic -er/-est, including double comparatives and qualifying expressions.

Errors still happen at B2, but they rarely cause misunderstanding. The goal is controlled, flexible use of language across social, academic, and professional settings.

How B2 fits in the CEFR progression

B2 builds directly on the foundations of B1 (Intermediate) and prepares you for C1 (Advanced). Many university entrance exams, professional certifications, and immigration requirements target B2 as the minimum standard.

Self-check: If you can read a newspaper editorial, follow most of a TED talk without subtitles, and write a clear essay arguing a position — you're likely operating at B2.

Ready to test yourself? Try Is your English level B2/Upper Intermediate? or practise specific B2 grammar with challenges like Basics. Advanced Conditionals And "wish", Basics. Passive Voice, and Sequence of Tenses in Indirect Speech.

Difficulty: Hard

Hard difficulty. Difficulty levels represent author's opinion about how hard a question or challenge is.