Logic syntax defines the rules for constructing valid expressions in formal logical systems. Below is a structured overview of key elements in common logics, such as propositional and first-order logic.
## Propositional Logic
– Atomic Propositions: Basic statements represented by letters (e.g., p, q, r). These are the simplest units.
– Connectives:
– Negation: ¬p (not p)
– Conjunction: p ∧ q (p and q)
– Disjunction: p ∨ q (p or q)
– Implication: p → q (if p then q)
– Biconditional: p ↔ q (p if and only if q)
– Well-Formed Formulas: Expressions formed by combining atomic propositions with connectives, following operator precedence (e.g., ¬p ∧ q is valid).
## First-Order Logic
– Terms:
– Constants: Fixed values (e.g., a, b).
– Variables: Placeholders (e.g., x, y).
– Functions: Operations on terms (e.g., f(x) for a function f applied to x).
– Predicates: Statements about terms (e.g., P(x) means “x has property P”).
– Quantifiers:
– Universal: ∀x (for all x)
– Existential: ∃x (there exists x)
– Well-Formed Formulas: Built from predicates, terms, and quantifiers, combined with connectives (e.g., ∀x (P(x) → Q(x))).
## General Rules
– Parentheses: Used for grouping (e.g., (p ∧ q) ∨ r to specify order).
– Syntax Validity: Formulas must adhere to formation rules to avoid ambiguity; for example, quantifiers must bind variables properly.
This overview covers foundational syntax; extensions exist in modal, temporal, or programming logics like Prolog.
Table of Contents
- Part 1: OnlineExamMaker – Generate and Share Logic Syntax Quiz with AI Automatically
- Part 2: 20 Logic Syntax Quiz Questions & Answers
- Part 3: OnlineExamMaker AI Question Generator: Generate Questions for Any Topic

Part 1: OnlineExamMaker – Generate and Share Logic Syntax Quiz with AI Automatically
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Part 2: 20 Logic Syntax Quiz Questions & Answers
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Question 1:
What is the truth value of the proposition (p ∧ q) when p is true and q is false?
A. True
B. False
C. Undefined
D. Both true and false
Answer: B
Explanation: The conjunction (AND) operator requires both operands to be true; since q is false, the entire expression is false.
Question 2:
In propositional logic, which symbol represents the negation operator?
A. ∧
B. ∨
C. ¬
D. →
Answer: C
Explanation: The symbol ¬ is used to denote negation, which inverts the truth value of the proposition it precedes.
Question 3:
What is the result of the disjunction (p ∨ q) if p is false and q is true?
A. True
B. False
C. Undefined
D. Both true and false
Answer: A
Explanation: The disjunction (OR) operator is true if at least one operand is true; here, q is true, so the result is true.
Question 4:
Which of the following is a tautology?
A. p ∧ ¬p
B. p ∨ ¬p
C. p → ¬p
D. p ↔ ¬p
Answer: B
Explanation: The law of excluded middle states that p ∨ ¬p is always true, regardless of the truth value of p.
Question 5:
In predicate logic, what does ∀x P(x) mean?
A. There exists an x such that P(x) is true
B. For all x, P(x) is false
C. For all x, P(x) is true
D. There exists no x such that P(x) is true
Answer: C
Explanation: The universal quantifier ∀ means “for every x,” so ∀x P(x) asserts that P(x) holds true for all values of x.
Question 6:
What is the contrapositive of the implication p → q?
A. q → p
B. ¬q → ¬p
C. ¬p → ¬q
D. p ∧ ¬q
Answer: B
Explanation: The contrapositive of p → q is formed by negating and swapping the antecedent and consequent, resulting in ¬q → ¬p.
Question 7:
Which logical equivalence is represented by De Morgan’s law: ¬(p ∧ q)?
A. ¬p ∨ ¬q
B. ¬p ∧ ¬q
C. p ∨ q
D. p ∧ q
Answer: A
Explanation: De Morgan’s law states that the negation of a conjunction is equivalent to the disjunction of the negations: ¬(p ∧ q) ≡ ¬p ∨ ¬q.
Question 8:
If p is true and q is true, what is the truth value of p ↔ q?
A. True
B. False
C. Undefined
D. Depends on context
Answer: A
Explanation: The biconditional (↔) is true when both propositions have the same truth value; since both p and q are true, it is true.
Question 9:
In a truth table for p → q, when is the implication false?
A. p is true and q is true
B. p is false and q is true
C. p is true and q is false
D. p is false and q is false
Answer: C
Explanation: An implication p → q is false only when the antecedent p is true and the consequent q is false.
Question 10:
What is the existential quantifier symbolized as?
A. ∀
B. ∃
C. ¬
D. ∧
Answer: B
Explanation: The existential quantifier ∃ means “there exists at least one x such that,” indicating the presence of at least one instance.
Question 11:
Which of the following is logically equivalent to p ∨ q?
A. ¬(¬p ∧ ¬q)
B. ¬(¬p ∨ ¬q)
C. ¬p ∧ ¬q
D. p ∧ q
Answer: A
Explanation: By De Morgan’s law, ¬(¬p ∧ ¬q) simplifies to p ∨ q, showing their logical equivalence.
Question 12:
In logic, what does a contradiction represent?
A. A statement that is always true
B. A statement that is always false
C. A statement that can be either true or false
D. A statement dependent on variables
Answer: B
Explanation: A contradiction, like p ∧ ¬p, is a proposition that yields false for all possible truth values.
Question 13:
For the proposition ∃x (P(x) ∧ Q(x)), what must be true?
A. P(x) is true for all x
B. Q(x) is false for all x
C. There is at least one x where both P(x) and Q(x) are true
D. P(x) and Q(x) are never true together
Answer: C
Explanation: The existential quantifier ∃ requires that there exists at least one x satisfying both P(x) and Q(x).
Question 14:
What is the result of applying the implication rule to p and p → q?
A. q
B. ¬q
C. p ∧ q
D. ¬p
Answer: A
Explanation: Modus ponens states that from p and p → q, we can infer q as the conclusion.
Question 15:
Which connective is associative?
A. ∧
B. →
C. ¬
D. ↔
Answer: A
Explanation: Conjunction (∧) is associative, meaning (p ∧ q) ∧ r is equivalent to p ∧ (q ∧ r).
Question 16:
In predicate logic, what is the scope of a quantifier?
A. The entire formula
B. The part of the formula where the variable is bound
C. Only the predicate
D. The constants used
Answer: B
Explanation: The scope of a quantifier is the subformula in which the quantified variable is bound and has meaning.
Question 17:
If p is false, what is the truth value of ¬p?
A. True
B. False
C. Undefined
D. Depends on q
Answer: A
Explanation: Negation (¬) flips the truth value; if p is false, ¬p is true.
Question 18:
What is a contingency in logic?
A. A statement that is always true
B. A statement that is always false
C. A statement that can be true or false depending on the values
D. A statement with no truth value
Answer: C
Explanation: A contingency is a proposition that is neither a tautology nor a contradiction, meaning it can be true under some conditions and false under others.
Question 19:
Which of the following is an example of a valid syllogism?
A. All A are B; Some C are not A; Therefore, Some C are B
B. All men are mortal; Socrates is a man; Therefore, Socrates is mortal
C. No dogs bark; Fido is a dog; Therefore, Fido barks
D. Some birds fly; Penguins are birds; Therefore, Penguins fly
Answer: B
Explanation: This is a classic example of a valid categorical syllogism, following the rules of deduction.
Question 20:
In logic, what does the expression p XOR q represent?
A. p and q are both true
B. Either p or q is true, but not both
C. p and q are both false
D. p implies q
Answer: B
Explanation: Exclusive OR (XOR) is true when exactly one of the propositions is true, but not both.
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