Where is the light bulb in Microsoft word?

In Microsoft Word, the light bulb icon represents the "Smart Lookup" feature, which provides definitions, insights, and related information for selected text. You can find it in the "Review" tab on the Ribbon or by right-clicking on a Word or phrase and selecting "Smart Lookup" from the context menu. However, note that the exact appearance and availability of the light bulb may vary based on the version of Word you are using.