A bare infinitive is an infinitive without to, using the base form of the verb. Compare I saw her leave and I saw her leaving. Both are possible perception patterns, but they present the event differently. The first often presents it as a whole; the second usually highlights it in progress. This is a useful contrast in viewpoint, not a rule that the grammar alone proves exactly how long someone watched.
What a bare infinitive is within parts of speech
In She can swim, swim is a bare infinitive. In I made him apologise, apologise is a bare infinitive after make plus an object. A perception example is We watched the players warm up: watched carries tense, the players identifies the people perceived, and warm up describes their action. The second verb does not take the past ending from watched.
How verbs of perception use bare infinitives
In direct-perception patterns, see, hear, watch, feel and notice can be followed by an object and a bare infinitive or an -ing form. Compare I heard the baby cry and I heard the baby crying. The first often presents an event as a whole; the second can highlight an ongoing or repeated sound. Check the particular verb and context rather than treating these as interchangeable in every construction.
Meaning differences: bare infinitive versus present participle
Compare We watched the sun rise with We watched the sun rising above the hills. The first presents the event as a whole; the second focuses on it unfolding. This is a difference of viewpoint. Choosing one form does not by itself make a witness report more reliable or legally stronger. The account must state only what was actually observed.
Parts of speech connections across the sentence
Because this page is a hub for parts of speech, it is useful to map how each category contributes to these constructions. The perception verb is the finite verb. The person or thing perceived is usually a noun or pronoun. The bare infinitive is another verb form, but not a finite one. Adverbs may modify either the perception verb or the bare infinitive event: She clearly heard him speak softly. Adjectives can describe the object noun: We watched the nervous speaker begin. Prepositional phrases add setting: I saw them run across the field. Determiners and articles identify nouns: the speaker, an audience. Conjunctions coordinate phrases and clauses: I saw him open the gate and wave. Interjections rarely matter syntactically, but they often appear in reported speech around perception events. Understanding parts of speech at this level helps learners parse sentence roles accurately. It also supports related grammar topics such as direct objects, complements, phrasal verbs, nonfinite clauses, and verb patterns after causative and modal verbs.
Common verbs, patterns, and examples
Use the table to compare several patterns. A perception construction, a causative construction and a modal construction have different triggers, even when each contains a base-form verb. Do not extend one pattern to every verb.
| Trigger verb or category | Pattern | Example | Meaning note |
|---|---|---|---|
| Perception verb | verb + object + bare infinitive | I saw her cross the road. | Direct perception of a complete event. |
| Perception verb | verb + object + present participle | I saw her crossing the road. | Action viewed as ongoing. |
| Causative make | verb + object + bare infinitive | The joke made him laugh. | Cause or compel an action. |
| Modal verb | modal + bare infinitive | She can drive. | No to after central modals. |
| Help | verb + object + bare infinitive / to-infinitive | They helped us move. | Both forms are standard, with slight style variation. |
Grammar standards, variation, and frequent mistakes
In an active direct-perception example, use They saw him leave, not They saw him to leave. A corresponding passive can be He was seen to leave; an -ing passive is also possible: He was seen leaving. Keep the object pronoun in the active example: him, not he. A mental-state verb may require another pattern, as in I knew that he had won. Check the verb’s dictionary entry.
How this topic connects to the wider grammar hub
Compare the patterns in Cambridge’s perception-verb guide. After can or could plus hear or see in this direct-perception construction, use the -ing form: I can hear someone singing. For causative make, compare They made us wait with We were made to wait, as illustrated in the British Council infinitive reference.
Practise the verb together with its pattern. Compare see someone leave, see someone leaving and want someone to leave. Keep the intended meaning in view. The infinitive itself does not change for person or tense in these examples; the first verb carries tense. Check a learner dictionary when you change the first verb or the voice.
Frequently Asked Questions
What is a bare infinitive, and why does it appear after verbs of perception?
A bare infinitive is the base form of a verb used without to. In sentences such as I saw her leave, We heard them sing, and They felt the ground shake, the words leave, sing, and shake are bare infinitives. They follow verbs of perception like see, hear, feel, watch, and notice when the speaker is describing a directly perceived action or event.
This pattern matters because it shows how English organizes meaning through sentence structure. The perception verb introduces the act of sensing, the noun or pronoun after it identifies what was perceived, and the bare infinitive names the action perceived: I saw her leave means that I perceived the event of her leaving. Grammatically, the object of the first verb also functions as the understood subject of the second verb. In I heard them sing, them is the object of heard and at the same time the performer of sing.
For practice, underline the first verb, circle the object noun or pronoun, and identify the second verb form. In I heard them sing, heard is finite and them identifies who sang. Then write a second example with a different object pronoun.
How is a bare infinitive after a perception verb different from a present participle in the same position?
The bare infinitive often presents an action as a whole event: I saw her leave. The -ing form typically presents it as ongoing: I saw her leaving. The contrast can be subtle. Describe it as a difference in how the event is presented, rather than a guarantee that every stage of a long event was witnessed.
By contrast, the present participle often emphasizes the action as ongoing, in progress, or unfolding at the moment of perception. I saw her leaving focuses more on the process than on the complete event. In many contexts the difference is subtle, and native speakers may choose one or the other depending on what they want to highlight. Still, the general distinction is useful: bare infinitive for the whole event, -ing form for the ongoing action.
The same principle appears in many examples: We heard them sing can suggest that we heard the performance as an event, while We heard them singing may emphasize the sound in progress. She felt the house shake presents a complete perceptible event; She felt the house shaking gives more attention to duration or unfolding movement. For learners, the best approach is not to memorize an absolute rule, but to understand the difference in viewpoint. English often lets speakers choose the form that best matches how they are mentally framing what they perceived.
Which verbs commonly take this pattern, and what sentence structure do they follow?
The most common verbs in this pattern are verbs of perception, especially see, hear, feel, watch, notice, and sometimes observe. These verbs are used when someone directly perceives another person, thing, or event. The basic structure is: subject + perception verb + object + bare infinitive. For example: I saw him run, They heard the baby cry, She felt the floor move.
That structure is important because the noun phrase in the middle has two jobs at once. It is the object of the perception verb, but it is also the understood subject of the bare infinitive. In We watched the children play, the children are what we watched, and they are also the ones performing the action play. This dual relationship is one reason the pattern is so useful in grammar teaching: it makes visible the way English can compress meaning into a compact clause-like structure without needing a separate finite verb form.
Pronoun case also matters here. Standard English uses object pronouns after the perception verb: I saw him leave, not I saw he leave. The same applies to her, them, and us. Learners should also notice that the bare infinitive does not change for tense, number, or person. The tense is carried by the first verb, not the second. In I saw her leave yesterday, the past meaning comes from saw; leave remains in its uninflected base form.
Why do we say “I saw her leave” instead of “I saw her to leave”?
We say I saw her leave because this construction requires a bare infinitive, not a full infinitive with to. English allows certain verbs to be followed directly by the base form of another verb, and perception verbs are a major group in which this happens. After see, hear, feel, and similar verbs, the language conventionally uses the uninflected verb stem when the meaning is one of direct perception: I heard him speak, She watched them cross the street, We felt the building sway.
This is not random. It reflects a broader pattern in English syntax in which some verbs license bare infinitives and others require to-infinitives. For example, we say I want her to leave because want takes a different complement pattern. But with a perception verb, the direct-perception structure normally excludes to. That is why I saw her to leave sounds ungrammatical in standard English.
Learn a sentence frame with each verb: see someone do something, see someone doing something and want someone to do something. Compare the meaning and the second verb form. Keep one correct example with each new verb in your study notes.
What are the most common learner mistakes with bare infinitives after perception verbs?
One common mistake is adding to where it does not belong, as in I heard him to sing or We saw them to leave. In standard English, those forms are incorrect when the speaker means direct perception. The correct versions are I heard him sing and We saw them leave. This error often happens because learners overgeneralize from other verb patterns, especially ones like want someone to do something or need someone to do something.
Another frequent problem is using the wrong pronoun form. Because the noun or pronoun after the perception verb is the object of that verb, standard usage requires object forms: me, him, her, us, and them. So we say She saw me fall, not She saw I fall. Learners also sometimes confuse the bare infinitive with the -ing form and use one where the other would express a different nuance. While both can be grammatical, choosing between them affects how the event is viewed, so awareness of that distinction leads to more precise and natural English.
A third issue is misunderstanding the meaning of the construction. I saw him leave does not simply mean that I saw him and, separately, he left. It means I perceived the act of his leaving. Recognizing that integrated meaning is essential. The pattern is not just a vocabulary combination; it is a compact grammatical structure that encodes who did what and how the speaker came to know it. For that reason, the best practice is to study whole sentences, compare bare infinitive and -ing versions, and pay close attention to authentic examples in reading and listening. That approach helps learners move from rule memorization to real grammatical control.
Worked sentence comparisons
Worked comparison: “I saw Lina cross the bridge” presents the crossing as a whole. “I saw Lina crossing the bridge” focuses on it in progress. Neither sentence gives an exact observation duration.
Worked pattern check: “I heard someone sing” uses an object and bare infinitive. “I could hear someone singing” uses the -ing form after could hear. Keep the pattern with the first verb rather than adding to automatically.
