# 039. Name modules and the source files containing them consistently, with one module per file
topic: {ref}`modules`
The convention @Beliavsky uses is that a module named `m_mod` is defined in a source file `m.f90`.
That way if you see
```fortran
use m_mod, only: foo
```
in the code you know to look in `m.f90` for the definition of `foo`[^c].
This also helps to avoid name clashes, since otherwise
"it is quite frequent to have a procedure with the same name,
or a type with the same name as the module"[^a][^b].
This type of convention is not uncommon. For example:
- Curcic's *Modern Fortran* ([code examples](https://github.com/modern-fortran)),
where the modules are named `mod_` and the files `mod_.f90`
- The [Community Land Model](https://github.com/ESCOMP/CTSM/tree/master/src),
where *some* module names and their source file names are suffixed with `Mod`,
or `Type` if the main purpose of the module is to define a single type
- @everythingfunctional [recommends](https://everythingfunctional.gitlab.io/fortran-style-guide/)
suffixing module names with `_m` (and types with `_t`) and naming the source file with
suffix `_m.f90`
Additional recommendations:
- > Prefix module names with the library name to avoid name clashes
> when used as dependency in other projects
---
```{note}
Similar to the `_mod` module naming convention, since Fortran code is case-insensitive,
a convention for naming types is to use `_type`.
```
[^a]:
[^b]:
[^c]: Note that modern development environments, like [this VS Code extension](https://marketplace.visualstudio.com/items?itemName=hansec.fortran-ls)
will generally provide go-to-definition functionality.
---