Final answer:
Language etiquette is the practice that describes the importance of following grammar rules and avoiding abbreviations in business communications.
Step-by-step explanation:
The practice that describes the importance of following the rules of grammar and capitalization, avoiding abbreviations, and using respectful language in business communications is Language etiquette. Effective communication in the workplace involves being clear, concise, and using proper language proficiency and professional communication skills. Language etiquette helps individuals fit into new workplaces and convey a professional image to co-workers and clients.