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Choose the correct phrase to complete the roommate's party-planning checklist.

Before the guests arrive on Friday, we definitely need to _____ by a professional service. This place is a mess!

The correct answer is have the carpets cleaned.

After "need to," we use the base form of the verb. The causative structure requires have + object (the carpets) + past participle (cleaned).

"Clean the carpets" would mean the roommates are doing the scrubbing themselves, but the sentence specifies it will be done "by a professional service."

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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.

Modal Verb

English has the modal verbs can, could, may, might, must, shall, should, will, would, and also (depending on classification adopted) ought (to), dare, need, had (better), used (to). These do not add -s for the third-person singular, and they do not form infinitives or participles; the only inflection they undergo is that to a certain extent could, might, should and would function as preterites (past tenses) of can, may, shall and will respectively.

A modal verb can serve as the finite verb introducing a verb catena, as in "he might have been injured then". These generally express some form of modality (possibility, obligation, etc.), although will and would (and sometimes shall and should) can serve – among their other uses – to express future time reference and conditional mood.

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.

Participle

Participles are verb forms that do double duty — they help build tenses and voices, but they also work as adjectives and adverbs. Understanding both types of participles is essential for forming correct verb tenses, using the passive voice, and writing more sophisticated sentences.

The Two Participles

English has two participles:

  1. Present participle — formed by adding -ing to the base verb: doing, running, sleeping. It's identical in form to the gerund, but serves a different function (more on that below).
  2. Past participle — for regular verbs, it's the -ed form (walked, boiled). For irregular verbs, it varies widely: done, written, sung, gone.

How the Present Participle Is Used

  • Progressive tenses: She is reading a book.
  • As an adjective: The woman sitting by the window is my boss.
  • As an adverb: Looking up from his phone, he noticed the bus had arrived.
  • In absolute constructions (with its own subject): The weather being terrible, we cancelled the trip.

Present participles used as adjectives carry an active meaning — an exciting movie is one that excites you.

How the Past Participle Is Used

  • Perfect tenses: They have finished the project.
  • Passive voice: The email was sent this morning.
  • As an adjective: The broken window needs replacing.
  • Adverbially: Exhausted from the hike, we fell asleep immediately.

Past participles used as adjectives usually carry a passive meaning — the attached file is one that has been attached. However, past participles of intransitive verbs can have active meaning: fallen leaves (leaves that have fallen).

Participle vs. Gerund

Both the present participle and the gerund end in -ing, but they do different jobs. The participle acts as an adjective or adverb; the gerund acts as a noun.

  • Swimming in the lake, she felt completely free. (participle — describes she)
  • Swimming is her favourite hobby. (gerund — subject of the sentence)

The famous example Flying planes can be dangerous is ambiguous: flying could be a gerund ("the activity of flying planes") or a participle ("planes that fly").

Self-check: If you can replace the -ing word with a noun like "it" or "the activity," it's a gerund. If it describes a noun or tells you more about an action, it's a participle.

Watch Out: Past Tense vs. Past Participle

For regular verbs, the past tense and past participle look the same (walked, played). For many irregular verbs, they differ:

  • ✅ I went home early. (past tense)
  • ✅ I have gone home early. (past participle)
  • ❌ I should have went home early.

If you're unsure, check whether the verb follows a helping word like have, has, or had — if it does, you need the past participle form.

Ready to practise? Try Gerund vs. Participle: Understanding -ing Word Functions, Participle Clauses: Shortening Sentences with -ing and Having + Past Participle, or Participle vs Gerund.

Phrase

In everyday speech, a phrase may be any group of words, often carrying a special idiomatic meaning; in this sense it is synonymous with expression. In linguistic analysis, a phrase is a group of words (or possibly a single word) that functions as a constituent in the syntax of a sentence, a single unit within a grammatical hierarchy. A phrase typically appears within a clause, but it is possible also for a phrase to be a clause or to contain a clause within it.

B1 | Intermediate

B1 is the intermediate level of the Common European Framework of Reference for Languages (CEFR). It marks the point where you move beyond survival English and start expressing yourself with real independence — describing experiences, explaining opinions, and handling everyday situations without a script.

What a B1 user can do

At this level, you're expected to:

  • Understand the main points of clear, standard speech and writing on familiar topics — work, school, travel, hobbies.
  • Handle most travel situations in English-speaking environments.
  • Produce simple connected text on topics you know or care about.
  • Describe experiences, events, hopes, and plans, and give brief reasons and explanations for your opinions.
  • Communicate in routine tasks that require a straightforward exchange of information.

What B1 grammar looks like

B1 is where grammar starts to get more layered. You're not just forming basic sentences anymore — you're combining ideas, using different tenses with more precision, and starting to handle structures like the passive voice, modal verbs for necessity and possibility, and gerunds vs. infinitives. You're also expected to build complex sentences with linking words and dependent clauses.

Typical B1 grammar areas include:

  • Future tenses — distinguishing will, going to, and the present continuous for future plans
  • Passive voiceThe report was written yesterday.
  • Modal verbsYou should apply early. / She might be late.
  • Used toI used to live in Berlin.
  • Verb patterns — knowing whether a verb takes a gerund, an infinitive, or both (I enjoy reading vs. I decided to leave)

What B1 doesn't mean

B1 speakers still hesitate, make grammatical errors, and sometimes struggle with less familiar topics. That's normal. The key difference from A2 is that you can keep a conversation going and get your point across even when things aren't perfect. The step up to B2 involves handling more abstract topics, understanding nuance, and producing more complex, accurate language.

Self-check: Can you tell a friend about a recent trip — what happened, what you liked, and what you'd do differently — without switching to your native language? If yes, you're likely operating at B1 or above.

Ready to find out where you stand? Try Are you B1/Intermediate? Test your English CEFR Level to figure out!, then build your skills with challenges like Basics. Passive Voice, Basics. Modal verbs, and Used to.

Difficulty: Medium

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