{% hint style="info" %}
If this is your first time defining a Unit, we recommend reading the [**Introduction to Units**](/units/introduction-to-units.md) first
{% endhint %}
You will most commonly define [**Units**](/units/introduction-to-units.md) as part of the [**Variable wizard**](/variables/variable-basics/unit-and-calculations.md). You will only need to define a Unit if your Variable is an `Assumptions` Variable, or if you select the `Specify Unit` option for a `Calculation` Variable.
The Unit step is simply a list of [**Unit Parts**](/units/key-unit-concepts.md#compound-units), in a standard [**List View**](/using-taglo-software/the-taglo-interface/list-views.md), in which you can *Add*, *Edit* and *Duplicate* Unit Parts. The resulting Unit is shown as a formula at the top of the step.
Each Unit Part can be edited in a separate wizard, or specific properties can be edited individually by clicking on one of the shortcut buttons displayed.
Shortcut buttons (as per above image)
* Change the base [**Tag**](/tags/introduction-to-tags.md) and/or [**Unit Factor**](/units/advanced-units.md#factors)
* Change the Order
* Change the Time Type (`Flow`, `Balance`, `Flow (Constant)`, `Balance (Constant)`
* `Change the Time Offset`
* `Add a Context modifier`
* Multiply the Order by -1
* Make a copy of the Unit Part
{% hint style="info" %}
Functionality of the Unit step depends on the context. You will find additional options if your Variable has [**Dimensions**](/dimensions/introduction-to-dimensions.md), or if you are creating a [**Data Point**](/assumptions/assumptions-wizard/linking-to-external-data.md) from scratch.
These differences are covered in the relevant sections of documentation.
{% endhint %}
## Default Unit
You can set a default Unit for new Variables by navigating to [**Model Settings**](/models/model-editor.md#model-settings)**.**
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