Superlative form of long, indicating the greatest length or duration.

सबसे लंबा

English Usage: This is the longest river in the world.

Hindi Usage: यह दुनिया की सबसे लंबी नदी है।

In some contexts, can refer to the most extended period of time or duration.

सबसे लंबा समय

English Usage: The longest I’ve waited is around two hours.

Hindi Usage: मैंने सबसे लंबे समय तक दो घंटे तक इंतजार किया है।