Effective communication is crucial in the UPSC interview process because it helps candidates articulate their ideas clearly and confidently. Interviewers assess not only a candidate's knowledge but also their ability to convey information succinctly and persuasively. Good communication skills reflect a candidate's potential to represent the government effectively and engage with the public. Additionally, candidates must understand the nuances of body language and active listening, which contribute to forming a positive impression and establishing rapport with the interview panel.