The sentence is the fundamental unit of communication in English. All written and spoken language — from a casual text message to a doctoral thesis — is ultimately constructed from sentences. Yet defining the sentence precisely is more complex than it first appears (Huddleston & Pullum, 2019, p. 85).
A traditional definition states that a sentence is "a group of words expressing a complete thought." While useful as a starting point, this definition is insufficient for grammatical analysis because it relies on the intuitive notion of "completeness" rather than on structural criteria (Quirk et al., 2018, p. 44). A more rigorous definition requires that a sentence must contain at minimum:
Definition and Minimum Requirements
The Sentence — Formal Definition
A grammatically complete unit of language that contains at minimum a subject and a finite verb, expresses a proposition, and is capable of standing alone as an utterance (Biber et al., 2021, p. 89).
Subject
The noun phrase about which the predicate makes a statement. Every sentence must have a subject — though in imperative sentences, the subject you is typically implied rather than stated (Crystal, 2019, p. 106).
Finite Verb
A verb that is marked for tense and agrees with its subject in person and number. A group of words lacking a finite verb — however long — is a phrase or clause, not a sentence (Huddleston & Pullum, 2019, p. 87).
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Key Test: Ask two questions — (1) Is there a finite verb? (2) Does the verb have a subject? If both answers are yes, the unit is a sentence. "Running through the hall" fails Test 1 — no finite verb. "Which the committee approved" fails Test 2 — no independent subject-verb pairing (Quirk et al., 2018, p. 46).
Section II
Types of Sentences by Structure
Sentences are classified structurally according to the number and type of clauses they contain. This classification determines the syntactic complexity of the sentence and has direct implications for academic writing style (Swales & Feak, 2020, p. 38).
Figure 4: The four structural types of English sentences, showing their clause composition. Adapted from Huddleston & Pullum (2019, p. 92) and Quirk et al. (2018, p. 48).
Type 1
Simple Sentence
One independent clause only. May have a compound subject or compound predicate but remains structurally simple (Biber et al., 2021, p. 96).
"The professor submitted the report." · "Ahmed and Fatima passed the examination."
Formula: [Independent Clause]
Type 2
Compound Sentence
Two or more independent clauses joined by a co-ordinating conjunction (FANBOYS) or semicolon. Each clause could stand alone (Quirk et al., 2018, p. 52).
"The data was collected, but the analysis was incomplete." · "He wrote the draft; she revised it."
Formula: [IC] + co-ordinator + [IC]
Type 3
Complex Sentence
One independent clause and one or more dependent (subordinate) clauses, introduced by subordinating conjunctions or relative pronouns (Crystal, 2019, p. 111).
"Although the result was unexpected, the methodology was sound." · "The student who scored highest received a scholarship."
Formula: [IC] + [DC] (in any order)
Type 4 — Advanced
Compound-Complex Sentence
Two or more independent clauses AND one or more dependent clauses. The hallmark of advanced academic prose, allowing simultaneous expression of multiple logical relationships (Swales & Feak, 2020, p. 45).
"Although the sample was small, the findings were significant, and the paper was accepted for publication."
Formula: [IC] + [DC] + co-ordinator + [IC]
Section III
Types of Sentences by Function
Every sentence is also produced for a communicative purpose — a function. English recognises four functional sentence types. These cut across structural types: a simple sentence can be declarative, interrogative, imperative, or exclamatory (Crystal, 2019, p. 114).
Type
Function
Form Marker
Example
Declarative
States a fact, opinion, or piece of information. The dominant type in academic writing (Biber et al., 2021, p. 118).
Subject precedes finite verb
"The study confirmed the hypothesis."
Interrogative
Asks a question, inviting a response or information (Quirk et al., 2018, p. 58).
Auxiliary precedes subject (Yes/No); Wh-word at front (Wh-question)
"Did the results support the theory?" / "What caused the anomaly?"
Imperative
Issues a command, instruction, or request. Subject you is omitted (Huddleston & Pullum, 2019, p. 95).
Base form of verb; no stated subject
"Read the passage carefully." / "Consider the following evidence."
Exclamatory
Expresses strong emotion or surprise. Rare in formal academic writing (Crystal, 2019, p. 115).
Introduced by What or How
"What a remarkable contribution this study has made!"
Section IV
Parts of the Sentence — Subject and Predicate
Every sentence divides into two major constituents: the subject and the predicate. This binary division is the most fundamental grammatical analysis a student can perform on any sentence (Quirk et al., 2018, p. 66).
Subject and Predicate — Definitions
Subject
The noun phrase that the sentence is about. It is the topic of the predicate's statement. In declarative sentences, the subject typically appears before the finite verb. The subject controls verb agreement — it determines whether the verb is singular or plural (Huddleston & Pullum, 2019, p. 100).
Predicate
Everything in the sentence that is not the subject — the finite verb and all that accompanies it. The predicate makes a statement, asks a question, or gives a command about the subject (Biber et al., 2021, p. 125).
"The senior lecturer published a comprehensive textbook last year."
SubjectThe senior lecturer
Noun phrase — controls verb agreement
Predicatepublished a comprehensive textbook last year
Everything said about the subject
Within the predicate, it is possible to identify further components — the verb, the object, and the complement. Each plays a distinct grammatical role (Crystal, 2019, p. 107).
Section V
The Verb
The verb is the core of the predicate — the element without which no predicate can exist. Every complete sentence contains at least one finite verb (Biber et al., 2021, p. 127). For the purposes of sentence analysis, verbs are classified by the type of structure they require:
Verb Type
Definition
Requires
Example
Transitive
Carries action from the subject to an object — the action passes across to something (Quirk et al., 2018, p. 74).
A direct object to complete meaning
"She wrote a letter." — wrote is transitive; a letter is the object
Intransitive
Does not carry action to an object — the action remains with the subject (Huddleston & Pullum, 2019, p. 108).
No object; sentence is complete without one
"The child slept." / "The crowd cheered loudly."
Linking (Copular)
Connects the subject to a subject complement — describes or identifies the subject rather than expressing an action (Biber et al., 2021, p. 130).
A subject complement (not an object)
"The result seems conclusive." / "She became the director."
Common linking verbs include: be, become, seem, appear, feel, look, taste, smell, sound, grow, remain, stay, turn. They are crucially different from transitive verbs because what follows them is a complement, not an object (Crystal, 2019, p. 109).
Section VI
The Object — Direct and Indirect
When a transitive verb is used, the sentence requires an object — the noun phrase that receives or is affected by the action of the verb. English distinguishes between two types of object (Quirk et al., 2018, p. 80):
Direct Object and Indirect Object
Direct Object (DO)
The noun phrase that directly receives the action of the verb. Test: ask What? or Whom? after the verb — the answer is the direct object (Huddleston & Pullum, 2019, p. 112). Example: "She sent a letter." — What did she send? A letter.
Indirect Object (IO)
The noun phrase that indicates the recipient or beneficiary of the action — the entity for whom or to whom the direct object is given, sent, or shown (Biber et al., 2021, p. 133). The indirect object always co-occurs with a direct object and typically precedes it. Test: ask To whom? or For whom? Example: "She sent the dean a letter." — To whom did she send it? The dean.
"The registrar sent the students their examination timetables."
SubjectThe registrar
Agent performing the action
Verbsent
Transitive — requires both objects
Indirect Objectthe students
Recipient — to whom it was sent
Direct Objecttheir examination timetables
What was sent — receives the action
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Order Rule: When both a direct and indirect object are present without a preposition, the indirect object comes first: "Give me the report." When the preposition to or for is used, the direct object comes first: "Give the report to me." Both are grammatically correct (Quirk et al., 2018, p. 82).
Section VII
The Complement — Subject and Object Complement
A complement is a word or phrase that completes the meaning of the verb by describing or identifying either the subject or the object. Unlike an object, a complement does not receive an action — it provides information about an entity already mentioned in the sentence (Biber et al., 2021, p. 138). There are two types:
Subject Complement (SC)
A subject complement follows a linking verb and describes or identifies the subject. It may be a noun phrase, adjective phrase, or prepositional phrase (Huddleston & Pullum, 2019, p. 116).
"The new professor became the head of department."
SubjectThe new professor
Who the sentence is about
Linking Verbbecame
Connects subject to complement
Subject Complementthe head of department
Identifies the subject — answers "What did she become?"
Further examples of subject complements: "The result was conclusive." (adjective phrase) · "She remained the director for three years." (noun phrase) · "The food tastes bitter." (adjective) (Crystal, 2019, p. 110).
Object Complement (OC)
An object complement follows the direct object and describes or identifies it. It is related to the direct object in the same way a subject complement is related to the subject (Quirk et al., 2018, p. 88).
"The senate appointed Professor Nwosu the Vice-Chancellor."
SubjectThe senate
Agent performing the action
Verbappointed
Transitive verb
Direct ObjectProfessor Nwosu
Who received the appointment
Object Complementthe Vice-Chancellor
Identifies what the DO became
Further examples: "They found the report incomplete." (adjective OC) · "The committee elected her chairperson." (noun phrase OC) · "His speech left the audience speechless." (adjective OC) (Biber et al., 2021, p. 140).
Distinguishing Object from Complement
The Renaming Test
A complement renames or describes another element. A direct object receives an action. Ask: is this element saying something about the subject or object? If yes, it is a complement. If it independently receives an action, it is an object (Huddleston & Pullum, 2019, p. 118).
The Linking Verb Clue
Subject complements always follow linking verbs. If you can replace the verb with a form of be and the sentence still makes sense, the complement is a subject complement: "She became the director" → "She was the director." ✓
Section VIII
Practical Activity: Sentence Parsing
Sentence parsing — the systematic identification of each element in a sentence — is the core practical skill of grammatical analysis. A student who can parse accurately can diagnose any grammatical error in their own writing (Thornbury, 2019, p. 95).
Subject
Predicate
Verb
Direct Object
Indirect Object
Complement
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Practical Activity
Parse Each Sentence — Identify All Parts
For each sentence below, identify: (a) the Subject, (b) the Verb and its type (transitive / intransitive / linking), and (c) any Object (direct or indirect) or Complement (subject or object). Write your analysis in a table.
1
"The committee approved the proposal unanimously."
Identify subject, verb type, and direct object.
Transitive · DO
2
"Professor Bello gave the students their results."
Identify subject, verb, indirect object, and direct object.
Transitive · IO + DO
3
"The research findings appear inconclusive."
What type of verb is "appear"? What follows it?
Linking · SC
4
"The vice-chancellor declared the project a success."
What is the direct object? What does "a success" describe?
Transitive · DO + OC
5
"The students worked diligently throughout the semester."
Does "diligently" receive the action or modify the verb?
Intransitive
6
"The rector remained committed to the vision."
"Remained" — linking or transitive? What follows?
Linking · SC
7
"The board of governors elected Dr. Eze the new provost."
Identify subject, verb, direct object, and object complement.
Transitive · DO + OC
8
"She sent the editorial team the revised manuscript."
Two noun phrases after the verb — which is IO and which is DO?
Transitive · IO + DO
9
"The laboratory report sounded thoroughly convincing."
What kind of verb is "sounded"? Is "convincing" an object or complement?
Linking · SC
10
"The dean considered the submission premature."
"premature" follows the object "the submission" — what role does it play?
Transitive · DO + OC
Section IX
Conclusion & Key Takeaway
The sentence is not merely a string of words — it is a precisely organised grammatical structure, every element of which carries a specific syntactic function. The ability to distinguish subject from predicate, transitive from linking verb, direct from indirect object, and subject complement from object complement is the foundation of grammatical self-correction in academic writing (Quirk et al., 2018, p. 92).
A student who has internalised the parsing framework presented in this lecture can approach any sentence — in their own writing or in a scholarly text — and account for every element within it. This analytical rigour is what separates grammatically confident academic writers from those who write by intuition alone (Swales & Feak, 2020, p. 52).
Examination Questions
Lecture 2.5 — The Sentence: Definition, Types, and Parts
10 Questions · 20 Marks
1Multiple Choice
Which of the following is the most grammatically precise definition of a sentence?
A. Any group of words that begins with a capital letter and ends with a full stop
B. A group of words expressing a complete thought, however loosely defined
C. A grammatically complete unit containing at minimum a subject and a finite verb, capable of standing alone
D. A clause that is always introduced by a co-ordinating conjunction
[1 mark]
2Identify & Label
For each sentence, identify the Subject, the Verb (and its type), and either the Object or Complement as appropriate: (a) "The dean appointed Dr. Chukwu the new registrar." (b) "The results seemed surprisingly inconsistent." (c) "The lecturer gave the class their feedback."
[6 marks — 2 per sentence]
3Multiple Choice
In the sentence "The committee elected her chairperson," the word chairperson is:
A. A direct object receiving the action of the verb
B. An indirect object indicating the recipient
C. An object complement describing the direct object
D. A subject complement following a linking verb
[1 mark]
4Distinguish
Distinguish between a direct object and an indirect object. Write two original sentences — one using only a direct object and one using both a direct and indirect object. Label all elements.
[2 marks]
5Multiple Choice
Which of the following verbs is a linking verb?
A. write
B. conduct
C. become
D. submit
[1 mark]
6Write Out
Explain the difference between a subject complement and an object complement. For each type, write one original sentence and identify every part of the sentence.
[2 marks]
7Multiple Choice
A compound-complex sentence contains:
A. One independent clause only
B. Two or more independent clauses and no dependent clauses
C. One independent clause and one or more dependent clauses
D. Two or more independent clauses and one or more dependent clauses
[1 mark]
8Classify
Classify each sentence by both structural type and functional type, justifying each answer: (a) "Submit your assignment before the deadline." (b) "Although the funding was limited, the study succeeded, and the findings were published." (c) "Where did the research team conduct their fieldwork?"
[3 marks — 1 per sentence]
9Multiple Choice
In the sentence "The registrar sent the students their timetables," the indirect object is:
A. the registrar
B. sent
C. the students
D. their timetables
[1 mark]
10Short Essay
In a paragraph of 6–8 sentences, explain why the ability to identify the parts of a sentence — subject, predicate, verb, object, and complement — is described as foundational to grammatical accuracy in academic writing. Use specific examples of errors that arise from misidentifying these elements.
[2 marks]
References
Adewole, L. O. (2020). Syntactic complexity in the academic writing of Nigerian university students. Journal of Applied Linguistics and Language Research, 7(3), 58–74.
Biber, D., Johansson, S., Leech, G., Conrad, S., & Finegan, E. (2021). Longman Grammar of Spoken and Written English (2nd ed.). Pearson Longman.
Crystal, D. (2019). The Cambridge Encyclopedia of the English Language (3rd ed.). Cambridge University Press.
Dik, S. C. (2018). The Theory of Functional Grammar: The Structure of the Clause (reprint ed.). De Gruyter Mouton.
Huddleston, R., & Pullum, G. K. (2019). A Student's Introduction to English Grammar (2nd ed.). Cambridge University Press.
Nwachukwu-Agbada, J. O. J. (2021). Sentence structure errors in undergraduate academic essays: A Nigerian university case study. African Journal of English Language Teaching, 5(1), 88–106.
Obi-Okoye, A. F. (2022). Syntactic interference and clause embedding in the writing of first-year students at Nigerian tertiary institutions. International Journal of English Language Education, 10(2), 141–158.
Quirk, R., Greenbaum, S., Leech, G., & Svartvik, J. (2018). A Comprehensive Grammar of the English Language (reprint ed.). Longman.
Swales, J. M., & Feak, C. B. (2020). Academic Writing for Graduate Students (4th ed.). University of Michigan Press.
Thornbury, S. (2019). An A–Z of ELT: A Dictionary of Terms and Concepts (2nd ed.). Macmillan Education.