# KeyError: 'font.size' is not a valid rc parameter. See rcParams.keys() for valid parameters.

- **ID:** `python/matplotlib-rcparams-typo-error`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Typo in rcParams key; correct key is 'font.size' but user might have typed 'font.size' with a dot (which is correct) or a misspelling like 'font.szie'. Actually 'font.size' is valid; the error occurs when the key is misspelled (e.g., 'font.szie' or 'fontsize').

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.7 | active | — | — |
| 3.8 | active | — | — |

## Workarounds

1. **Use the exact key from documentation** (95% success)
   ```
   plt.rcParams['font.size'] = 12
   ```
2. **List all rcParams to find the correct spelling** (90% success)
   ```
   print([key for key in plt.rcParams.keys() if 'font' in key])
   ```

## Dead Ends

- **Using 'fontsize' without dot** — The key must have a dot separating group and property; 'fontsize' is not valid. (90% fail)
- **Using 'Font.size' with capital letters** — Keys are case-sensitive; 'Font.size' is not valid. (85% fail)