ArcGIS Pro 2.7 API Reference Guide
Language Property (SpellChecker)
Example 

ArcGIS.Desktop.Framework.Utilities Namespace > SpellChecker Class : Language Property
Gets or Sets the Spellchecker language per RFC 3066. For example, use en-US for U.S. English or fr-FR for France French.
Syntax
public string Language {get; set;}
Public Property Language As String
Example
SpellChecker s = new SpellChecker(CultureInfo.CurrentCulture.IetfLanguageTag);
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

SpellChecker Class
SpellChecker Members