From Liquipedia Warcraft Wiki
Passive abilities will apply their effects as long as they are available. Passive abilities do not consume mana and sometimes have cooldowns.
Pseudo Random Distribution
- Main Article: Pseudo Random Distribution
Pseudo Random Distribution is a mechanic from the Warcraft 3 engine where seemingly random outcomes are instead pseudo-random, limiting the factor of luck significantly. Pseudo-random distributions are used to calculate chance based passive abilities including Critical Strike, Bash, Evasion and Drunken Brawler. The PRD works by increasing the percentage chance for an activation by a certain amount every time it didnt activate until the chance for activation is over 100%.