Skip spelling check for same text in PowerPoint
Like Microsoft Word, PowerPoint allows skipping such text when spell checking. For example, the word erors is skipped:

To skip selected text during spell checking, follow these steps:
1. Select the text you want to skip.
2. On the Review tab, in the Language group, select the Language list and then choose Set Proofing Language...:

3. In the Language dialog box, click the Do not check spelling checkbox:

4. Click OK.