You can use the taxonomy condition so that when a node is viewed with either a specific taxonomy term or a term from a particular vocabulary a context is activated.

If you wish to use the a vocabulary or its terms in this way you must first activate context on that taxonomy, to do so you will need to:

1. Go to the taxonomy settings page, Admin > Content Management > Taxonomy.
2. Find the vocabulary that you want to use and click 'edit vocabulary' in the 'operations' column.
3. Find the 'Include as context condition' check box and ensure it is ticked
4. Submit the form and you should now be able to use the taxonomy as a condition in your context definition.