# Defining a boundary

**URL:** <https://community.freefem.org/t/defining-a-boundary/1628>\
**Category:** General Discussion\
**Created:** [March 26, 2022, 10:20am UTC](https://community.freefem.org/t/defining-a-boundary/1628 "2022-03-26T10:20:25Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Jamal](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/jamal/32/1527_2.png) [@Jamal](https://community.freefem.org/u/Jamal)\
**Post date:** [March 26, 2022, 10:20am UTC](https://community.freefem.org/t/defining-a-boundary/1628/1 "2022-03-26T10:20:25Z")

</div>

hello everyone  
How to define the border \gamma(x) with the function border + buildmesh in freefem ?  
 ![gamma](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/8/8421cfebe73133180a18e97fc251cadcaa09e2b9.png)

---

<div class="post-metadata">

**Author:** ![julienG](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/julieng/32/222_2.png) [@julienG](https://community.freefem.org/u/julienG)\
**Post date:** [March 26, 2022, 3:10pm UTC](https://community.freefem.org/t/defining-a-boundary/1628/2 "2022-03-26T15:10:48Z")

</div>

something like

> border gamma (t=0,1){ label = your label;  
> x= t;  
> y= 1+0.1\*cos(2 \* pi \* t); }

---

<div class="post-metadata">

**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [March 27, 2022, 8:55am UTC](https://community.freefem.org/t/defining-a-boundary/1628/3 "2022-03-27T08:55:37Z")

</div>

see the example Ground water page 170 of [https://www.ljll.math.upmc.fr/hecht/ftp/ff++days/2021/FH-edp/ff-days-13.pdf](https://www.ljll.math.upmc.fr/hecht/ftp/ff++days/2021/FH-edp/ff-days-13.pdf) and the example [https://www.ljll.math.upmc.fr/hecht/ftp/ff++days/2021/FH-edp/edp2/freeboundary.edp](https://www.ljll.math.upmc.fr/hecht/ftp/ff++days/2021/FH-edp/edp2/freeboundary.edp)