There is, but it’s not a menu item or even labelled as such. It’s just a pattern of use:
You can correct suggestions manually
When autocorrect changes something incorrectly:
- Tap the underlined corrected word.
- Choose the proper spelling from the left of the suggestion bar.
Doing this repeatedly helps the system learn (slowly).
If it is still failing regularly, reset your keyboard dictionary (Settings > General > Transfer or Reset > Reset > Reset Keyboard Dictionary)