Explanation:

- Option 1: Arajak Tatva - This term refers to elements that disrupt societal order, often associated with unruly or anarchic behavior. This was not chosen as the Hindi Word of the Year in 2018.

- Option 2: Nari Shakti - This phrase translates to "women's power" and signifies the strength and empowerment of women. It was selected as the Oxford Dictionary's Hindi Word of the Year for 2018, reflecting the increased focus on women's rights and gender equality.

- Option 3: Sangathan - Meaning "organization" or "union," this word underlines the importance of unity and collective efforts. However, it was not the chosen word for 2018.

- Option 4: Navayuvak - This refers to "young person" or "youth," highlighting the significance of the younger generation. This was not the Word of the Year for 2018.