Buried in the privacy policy for Win 10 (expand the Input Personalization section) is:

You can turn off Input Personalization at any time. This will stop the data collection for this feature and will delete associated data stored on your device, such as your local user dictionary and your input history. As Cortana uses this data to help understand your input, turning off Input Personalization will also disable Cortana on your device. At https://www.bing.com/account/personalization, you can also clear data sent to Microsoft, such as your contacts and calendar data, user dictionary, as well as search and browsing history if your device also had Cortana enabled.

According to HowToGeek after installation you can disable this by:

If you have chosen express settings and you want to opt out of some or all of these, all is not lost. You can still go into the settings and change things.

To turn off the first item found in the Personalization settings, you will need to open the Privacy group in Settings and then “Speech, inking, & typing”.

Click or tap “Stop getting to know me”.

I'd strongly recommend disabling it the officially supported way over screwing with an executable. The latter runs both the risk that Windows repair or a future Windows update to Cortana will install a new executable and re-enable it without your knowledge, or that because you removed the file an the update will fail. With consumer versions of W10 not allowing you to opt out of patches this could result in you getting stuck in a reboot loop due to the patch failing to install or lock you out of future security updates because you don't have one of last month's required patches.

Buried in the privacy policy for Win 10 (expand the Input Personalization section) is:

You can turn off Input Personalization at any time. This will stop the data collection for this feature and will delete associated data stored on your device, such as your local user dictionary and your input history. As Cortana uses this data to help understand your input, turning off Input Personalization will also disable Cortana on your device. At https://www.bing.com/account/personalization, you can also clear data sent to Microsoft, such as your contacts and calendar data, user dictionary, as well as search and browsing history if your device also had Cortana enabled.

According to HowToGeek, after installation, you can disable this by:

If you have chosen express settings and you want to opt out of some or all of these, all is not lost. You can still go into the settings and change things.

To turn off the first item found in the Personalization settings, you will need to open the Privacy group in Settings and then “Speech, inking, & typing”.

Click or tap “Stop getting to know me”.

I'd strongly recommend disabling it the officially supported way over screwing with an executable. The latter runs both the risk that Windows repair or a future Windows update to Cortana will install a new executable and re-enable it without your knowledge, or that because you removed the file the update will fail. With consumer versions of W10 not allowing you to opt out of patches, this could result in you getting stuck in a reboot loop due to the patch failing to install or lock you out of future security updates because you don't have one of last month's required patches.