You can prevent AutoCorrect from correcting specific abbreviations or words that have mixed capital letters and lowercase letters.
තෝරන්න, ඊලඟට අයිකනය ක්ලික් කරන්න.
පහතින් ළුකක් කරන්න.
Type the abbreviation followed by a period in the Abbreviations (no subsequent capital) box and click New.
Type the word in the Words with TWo INitial CApitals box and click New.
To quickly undo an AutoCorrect replacement, press Command Ctrl+Z. This also adds the word or abbreviation that you typed to the AutoCorrect exceptions list.