No. Your notes are stored by Evernote in two locations: A local database on your device or computer, and the Evernote servers. As long as you are able to connect to the Evernote servers to sync your account, your notes and notebooks will be waiting for you in the cloud even if you uninstall.
Note: If you have opted to create any local notebooks, it's important to back these up before uninstalling Evernote or they will be lost. Learn more about local notebooks.
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