Decision
A point where the flow branches. The decision symbol is a diamond holding a question or condition, with one path leaving it for each possible answer, often labelled Yes and No.
Easily confused with
- RelationshipA relationship: how two or more entities are related, such as a customer who places an order. In Chen notation it is a diamond with the relationship’s name inside, joined by lines to the entities it relates.
- Decision and merge nodeBoth are diamonds where the flow branches; UML writes the conditions as guards on the outgoing lines.
How to read it
One line enters the diamond and two or more leave it. ISO 5807:1985 describes a single entry and a number of alternative exits, of which one and only one is taken after the condition inside is evaluated; the results, such as yes and no, may be written beside the lines. IBM’s manual lists what a program decision can test: a comparison, an indicator, a sign, a program switch. The 1970 American standard draws the diamond wider than it is tall, 1 to 2/3, and allows a branching table, a small table of conditions and the path for each, in place of the diamond.
Also searched as: decision symbol, diamond flowchart, flowchart decision.
Look-alikes
On an ER diagram a diamond is a relationship between entities, with no yes or no paths. In a UML activity diagram a diamond is a decision or merge node: the same idea, with the conditions written as guards on the outgoing lines.
Differences by standard
ISO 5807 allows more than two exits from one diamond. Under ANSI X3.5 each exit is identified with the logic path it stands for, and a plain Process rectangle may also stand in for a decision, since the basic process symbol covers deciding which way the flow goes.
Read next
- Next in Flowchart symbolsInput/output (data)Data going in or coming out: reading input or producing output, without saying on what medium. The input/output symbol is a parallelogram, a rectangle slanted to one side.
- In BPMN symbolsExclusive gatewayA point where the process takes exactly one of several paths. The exclusive gateway is a diamond, often with an X inside.
More flowchart symbols
The same shape elsewhere
Browse symbols drawn with arrows, diamonds or letters and numbers.
Sources
- Information processing: Documentation symbols and conventions for data, program and system flowcharts, program network charts and system resources charts, ISO 5807:1985, first edition (preview pages), International Organization for Standardization (iTeh Standards preview), Section 9.2.2.4
- Flowchart Symbols and Their Usage in Information Processing, ANSI X3.5-1970, adopted for federal use as FIPS PUB 24, American National Standards Institute; National Bureau of Standards (NIST), Sections 3.3.2.1, 4.10.2 and 4.11
- Flowcharting Techniques, IBM Data Processing Techniques, Form C20-8152, International Business Machines Corporation (bitsavers.org), Special processing symbols
- 10.3: Flowcharting, Kenneth Leroy Busbee, CSP31A C Programming, Delta College (LibreTexts Engineering), Decision
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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