Logical Reasoning
Disjunction (“or”)
A compound statement joined by “or”, true when at least one part is true.
| English | Disjunction (“or”) |
|---|---|
| Bahasa Melayu | Disjungsi ("atau") |
| 中文 | 析取（“或”） |
How it is used
The disjunction "6 is prime or 6 is even" joins two statements with "or". The first part is false but the second is true, so the whole disjunction is true, because a disjunction needs only one true part.
Where it shows up in SPM
Disjunction appears alongside conjunction in Form 4. Paper 1 asks for the truth value of an "or" statement or to identify a disjunction.
Paper 2 combines it with negation and quantifiers when building and evaluating compound statements.
Don't confuse it with
Open the chapter: Logical Reasoning →
Frequently asked questions
When is a disjunction false?
A disjunction "p or q" is false only when both parts are false. "9 is prime or 9 is even" is false, because 9 is neither prime nor even.
If either part is true, the whole disjunction is true.
Does "or" mean one or the other but not both?
In SPM logic, "or" is inclusive: it is true when one part is true and also when both are true. "4 is even or 4 is a perfect square" is true because both parts hold; the disjunction is only false when neither part is true.