In Microsoft Word, you can use the "Word Count" option to count the number of words in a document. The option can be found in the "Review" tab on the ribbon, typically located in the "Proofing" group. Once you click on the option, a Word Count dialog box will appear, showing the number of words, characters, paragraphs, and lines in the document.
Another way to count the words is by using the keyboard shortcut "Ctrl + Shift + G" (Windows) or "Command + Shift + G" (Mac) which will also open the Word Count dialog box.
It's also worth noting that, you can also select a section of text and right click, then select the option "Word Count" and it will give you the count of the selected text only.
Additionally, you can also use the Find and Replace feature to count the number of occurrences of a specific word or phrase in a document. To do this, go to "Home" tab, in the Editing group, click on "Replace" and in the find box enter the word or phrase you want to count, leave the "Replace with" box blank, then click on the "Find Next" button, it will highlight all the occurrences of the word or phrase, then you can see the number of occurrences in the bottom left corner of the window.