# Difference between 'Expression' and 'Statement' in Stan

**URL:** <https://discourse.mc-stan.org/t/difference-between-expression-and-statement-in-stan/15378>\
**Category:** General\
**Created:** [May 25, 2020, 4:51pm UTC](https://discourse.mc-stan.org/t/difference-between-expression-and-statement-in-stan/15378 "2020-05-25T16:51:53Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![stan\_beginer](https://avatars.discourse-cdn.com/v4/letter/s/f0a364/32.png) [@stan\_beginer](https://discourse.mc-stan.org/u/stan_beginer)\
**Post date:** [May 25, 2020, 4:51pm UTC](https://discourse.mc-stan.org/t/difference-between-expression-and-statement-in-stan/15378/1 "2020-05-25T16:51:53Z")

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Hi,

I am reading the reference manual of Stan and I feel confused about the difference between ‘expression’ and ‘statement’ in Stan. Although I know that they are referring to different things, is there more intuitive way to define their difference?

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**Author:** ![mitzimorris](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/mitzimorris/32/29_2.png) [@mitzimorris](https://discourse.mc-stan.org/u/mitzimorris)\
**Post date:** [May 25, 2020, 9:45pm UTC](https://discourse.mc-stan.org/t/difference-between-expression-and-statement-in-stan/15378/2 "2020-05-25T21:45:22Z")

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- An expression denotes a value.
- A statement causes some operation to be performed that changes state or affects control flow.

Evaluation of an expression requires computation. Execution of a statement changes program state in some way.

See [https://mc-stan.org/docs/2\_23/reference-manual/bnf-grammars.html](https://mc-stan.org/docs/2_23/reference-manual/bnf-grammars.html)